Is it this book? https://www.amazon.com/PADI-Sidemount-Tec-Diver-Manual/dp/B0186787YESo, I purchased the PADI sidemount course book, asked a bunch of questions, watched some videos, surfed the net, bought some gear, went to the local pool and did a bunch of drills and then went diving. Seemed to work just fine.
Because if so, I'd say you could have skipped the part about the book and simply look a lot around on the interwebz... (and yes, I'm judging a book by its cover, it seems very appropriate here)