There are several different books available including one that is sold by Sage. If you are interested in coming up to speed on the ACT! program, consider the ACT! for Dummies book. (In the interest of disclosure, I did the tech editing for that book and can vouch for its accuracy.) However, that book does not go into great depth but using it along with the ACT! help and knowledge base would be a good approach.
Roy Laudenslager ACT! Certified Consultant Techbenders firstname.lastname@example.org