This book is a rare gem from the days of old school grammar books in that it has an answer key. It is comprehensive enough that it could be your first book on grammar, but the diagramming portions are limited and not always "standard," so if you're looking for a book to learn sentence diagramming specifically, look elsewhere.
That being said, this book's section on infinitives really shines, and it might aid you in your understanding of diagramming once you've already learned the basics.
If this is your first book on diagramming and grammar, then Cindy Vitto's "Grammar By Diagram" is a logical next step. If you want to focus more on diagramming sentences, then consider Dr. Eugene Moutoux's "Drawing Sentences."