You can see a list of the base stats of an item in the shop window (one of the screenshots shows this off with a fist weapon that gives ATK+15, COUNTER+1). These are read directly from the item's properties. The stats an item gives are then multiplied with a character's aptitudes for those stats (so a character with 70% ATK aptitude would get 10 ATK from equipping that fist).
The game isn't finished, so I don't see the point of writing a guide book (especially considering it's not particularly popular). I don't really believe that there's a single recommended strategy, either... I just try to provide different scenarios for each battle and then it's up to your own wits and strategy to figure out how to overcome them. Having a guide book recommend stuff would just make players improvise less.
The game essentially is a Disgaea clone, there are 30 tiers of each item type (ranging from wooden swords to divine relics that can cut a planet in two with a single slice) plus 10 additional tiers that aren't part of the loot tables, which are used for unique items like the Blood and Morlia swords. Most of the stuff that's actually in the game database currently ends at tier 15, silver weapons... so it seems like I've not finished added everything I planned.
Here's a sample of the database, in case you want an idea about what the ultimate achieveable stuff you can get in the game currently is:
//RANK 15
itemname[494] = "Flamberge"
itemprice[494] = 150000
itemattri[494] = "ATK+995;HIT+100;RES_FIRE+30;POW_FIRE+30;"
itemlore[494] = "This sword was made famous by the Frankian fencing schools who gave all their teachers one of these swords. They're made using layered steel of two different types."
Items are randomly generated both as loot drops and in shops because I like randomly generated items, I'm not going to change that. (The items available in a shop is generated when the room loads and aren't stored anywhere, so storing them until some other trigger happens would mean extra effort).