AbyssalCraft is the mod which this book is used to guide you through. It's mainly focused on exploration, with 4 new dimensions you can explore.
The dimensions are reached through the use of "Gateway Keys", which are keys designed to create portals between dimensions (the 4th dimensions is reached by falling out of the 3rd).
The Overworld has been expanded with 6 new biomes: the Darklands (normal, plains, forest, highlands, mountain) and the Coralium Infested Swamp.
There's also 5 new types of stone and 15 new ores found throughout the Overworld and the dimensions.
Apart from exploration, AbyssalCraft introduces it's own type of magic, through the use or rituals in order to worship The Great Old Ones.
Apart from magic and exploration, there's also machines, allowing you to transmute, crystallize and materialize objects. There's also a coin engraver.