Is the book in English or Japanese? If it is in English, and if you think its not much to ask - could you share a page or two (picture) on something that you find interesting (game mechanics preferably)?
Well, it's an official Squaresoft guide for a game which was not released outside Japan, so take a guess which Lauguage it is written in. ^^ (The guide was released in 1993)
But even for non-japanese speakers, this guide might be worth at least a look. Therefore, I'm still gonna show you some pages.
I hope the quality is good enough. I resized the pics since I didn't want to link images with the size of over 5MB.
This is a page of the first and core section of the guide: The "Map File":

Generally, this chapter is the walkthrough which features pictures of every screen in the game. It is also explained what to expect, which treasure can be found and where the secret passages are (those will be drawn as red lines). While there is no Monster Guide, this section does warn the reader about certain monsters. Eg. on the bottom of this page, you can see Exdeath's Soul. The text should translate into something like: >>When you return here in the 3rd world, you may run into this strong enemy. He can finish off a party member in a single turn with "Reaper's Sword" and "Banish". Use holy elemental attacks like "Excalibur".<<
On the next page, it would show you Kuzar Beast with the description >>It has 5000 HP and is weak to wind<<
Also, every location (with the sole exception of Exdeath's Castle) is only shown once. So in this case, while showing you the 12 treasures (weapons), it is stated under the headline that you can't break the seals in the second world. In the same manner, the guide tells you in the section of "The North Mountain" to return there in the 3rd world to obtain Bahamut.
It is also noteworthy to take a look at the romanization of some locations, as this was the first translation of those. While some of this guide are identically used in the GBA-Translation "ウォルス" (worusu) --> "Walse", others were never used, like the one you kan see on the shown example page ("Koozer, the Sealed Castle"). Some of those are really wacky, like the great sea trench literally called "The Great Deep".
Also, very noteworthy, 2 treasures are missing! It's those 2 hidden troll treasures from the solitary island shrine. Ironically, this guide tells you where Mr. Clear's cave is. So the guide called "Perfect Conquest" leads you into this man showing you that you didn't collect all treasures, laughing right at your face :P - No, jokes aside, I'm sure many people involved in the game development didn't even know about those 2 troll treasures.
The "Map File" is interuppted 2 times by extra pages called "Extra Conquest". The 3rd "Extra Conquest" is located right at the end of the "Map File"

This is the first one. It features artwork of Amano and description of the Dawn Warriors (called "Four Braves of Dawn" here), Krile, Exdeath, Gilgamesh and Sage Ghido. I Guess Butz, Faris and Lenna are missing since they might already be described in the booklet of the game.
The 2nd Extra conquest shows you how to find and defeat Gogo, explains the Mimic job, how to acquire "Mighty Guard" and where Mr. Clear lives. The 3rd part exposes Omega's and Shinryu's stats and attacks and gives hints how to defeat them.
The second chapter is the "Item File"

It first shows weapons, followed by armor, accessory and consumables. Here you cann see the last weapons of the "Axes" section (Hammers are also counted as "Axes"), the 2 flail weapons (as said - according to the guide only equippable by White Mages and Berserkers) and the first Katana weapons. The box right next to the Attack/Battle Power value of the weapon is the "Element" box - the problem with that one is that there is no distinction between "Weapon is X-elemental" and "Weapon boosts X-Elemental spells". If at least one of those applies, the element is just put into the box without further explaination.
Also noteworthy: 2 Weapons are missing! Lenna's initial weapon, the Knife, and the Tinker Bell. The Thief Knife and the Man-Eater are listed at the end, out of every category. While it might be the right place for the Man-Eater, as it's only equippable by Dancers, I don't understand why Thief Knife is not listed alongside the other knives. It is also stated that it is equippable by all jobs but the White Mage.
Other mistakes include the alleged inability of the Ninjas to equip Armlets as well as the Giant's Glove boosting Speed and Magic by 5, rather than deducting 5, or messed up steal and drop information, most notably regarding the enemies in Phoenix Tower.
Following: the "Summoned Monster File"

It basically tells you how/where to acquire those and the effect. If you have to fight, it also exposes the Monster's stats. You can clearly see that the stats are absent for "Phoenix" in this page, as you don't fight it.
Next is the "Special Attack File", which is about enemies' attacks and magic (Blue Magic is included here)

The first column shows the attack's name, the second explains the effect, the third shows which monster uses it, and the fourth reveals the MP cost (only if it's a Blue Magic spell). Furthermore, you might see some circles in the 3rd column next to the monster names. The hollow circle means "Monster uses it normally", the filled one means "Used by releasing the monster after caught", and the circled circle/double circle means "Used by controlling the monster". The third column is incomplete and sometimes faulty.
The next pages contain charts for "Gaia", "Animals", "Sing", "Dance" and "Mix"



The next section is the bossguide - which is incomplete, because Exdeath (tree form) and Neo-Exdeath aren't even mentioned - it ends at Necrophobia!

And last, but not least: a list of all the Jobs' abilities:

It's not an ordinary list as you see the abilities are not explained. Instead, those are listed in a row, while all Jobs (except Freelancer and mimic) are listed in colums. The compatibility of every ability to every job is then rated with one of four symbols. Circled Circle/Double Circle = "strongly recommended ability for that job", Circle = "recommended ability for that job", Triangle = "Ability might be useful in certain situations" and X (for= "not recommended" (for simplicity, I will use the numbers 1-4 in my explainations with 1 being the best). For exapmle, "Equip Swords" scores 1 for Ninja because it increses his strength on top of being able to equip 2 swords, which are almost always stronger than knives, while on Knight, it scores 4 since Knights already can equip swords. "2-handed"/"Double Grip" scores 1 for the Knight - i don't have to explain why (^^) - and a measly 4 atfor Ninja - well you know that one too.
This section also holds some mysteries. The first one is the ability "2-Handed"/"Double Grip" - it scores 1 on the Jobs Knight, Berserker, Samurai, Mystic Knight, Blue Mage and Red Mage while scoring 2 on White and Time Mage and being rated with 4 on every other job. Pretty accurate on the first sight. But on the second thought: huh? Why scoring a 2 on Time Mage if the guide assumes he can't equip Flails? And even if the guide got the flail equipping jobs right this time - why is it rated 4 on the Chemist? It just doesn't make sense.
The other mystery is more interesting:

Without counting the first black row, pay attention to the 10th and 11th row. Those are the abilities of the Summoner Job (召喚士). The 10th is Summon (しょうかん) while the 11th is Call (よびだす). As you might see, the guide is implying the the summoner would have learned six abilities during the 3 Job levels! On level 1 Summon Lv1 and CallLv1, on level 2 SummonLv2 and CallLv2, on level 3 SummonLv3 and CallLv3 - simultaneous! To ensure that I didn't misunderstand, take a look at the Spellblade (まほうけん) ability (3rd row) - the numbers go from 2-7 as for job level, not 1-6 as for SpellbladeLv1-6.
So the questions I ask myself are: Is this just a mistake? If not, was there a time in development where gaining multiple abilities with 1 job level was being thought of? And also, what exactly would have been the differences between CallLv1, CallLv3 and the Call we know now?