I have been searching online for a book that teaches more in depth about Crystal Reports SQL formulas and I can't find much to choose from.

I can't say if my book is any good or not since I wrote it. But it's gotten great reviews on Amazon and people post good things about it on the forum as well. I have three chapters dedicated to how to write formulas as well as tutorials that walk you through common scenarios. The biggest difference is that since I get on the forum as much as my schedule allows, I get to see what everyone talks about as well as see what problems they have. Of course, if you aren't happy with the book, just send it back to Amazon (and please let me know why so I can make improvements in the next edition). And if you do like it, please post a review on Amazon as well. Since I'm a self-publisher, my only means of marketing the book is word of mouth.

Wait a minute. I take that back. My book covers writing formulas withing Crystal Reports using Crystal syntax or Basic syntax. This includes conditional formulas, record selection formula, etc. But I don't cover the syntax for writing formulas for Transact SQL. For that you would need a SQL specific book. Sorry.