Juliann Kost has a couple of videos on making custom templates in LR:
Personally, I find LR really deficient for Blurb bookmaking (if you want a custom book - it's pretty straightforward and easy to make a book but if you don't like what is in the app, you're out of luck).
I make may books in Photoshop because I need layers to make the pages I want (if I knew how to use InDesign or another design app, that would be the best way to go). That said, I still use LR ... I import all of my pages to LR just to add page numbers!! If you make full bleed pages in PS and then import them to Booksmart, you cannot number the pages with Booksmart (the numbers will be hidden beneath the full bleed page you import). So I find LR very useful, but only for a small part of the process. I then print the book to jpg and import to Booksmart in the normal fashion - I do this because there is no way to customize the covers and end flaps in LR...grrr... :-)
Good luck - maybe you can customize the LR templates enough for your purposes. If so, it will be a lot easier to make books.