But not every mod needs to start with books.. Botania has a crafting recipe for it's book, and it's recipes leading the front page before the DL I think. Thaumcraft's guidbook is explained how to be obtained before you download the mod aswell, in short.
Blood Magic could be obtained placing a book in a blood filled altar..
I feel like guidebooks took off with tinkers construct, but that book makes sense when you start out. It offer's a means of changing the early game. It provides crafting tables that can be made to hold items when you leave it's gui, it has a way to make repairable tools instead of continually crafting sticks, taking three pierces of whatever material, and making a new one, over and over and over again.
Meanwhile the openblocks book is a nice idea, but it would have merely been better off as something you craft, but see how to craft before installing the mod.