Using a Paperback Book
Yes, you can use a paperback book instead of a hardcover! It's not as easy and it doesn't look as good when you're done. The glue will warp the book slightly, especially the back cover. However, it is possible.
You can mostly follow the Basic Instructions, but there's a few things extra steps to take:
Before you start: make sure the cover has a laminate or plastic coating.
Not sure if it does? Drip some water onto the back; if it soaks in, don't use the book.
Why is that important? Because you're going to paint the inside with a huge amount of glue. Without that thin layer of plastic, the glue will soak right through the back cover and glue your book to whatever's under it.
During Steps 6-10: Be prepared to spend more time and effort cutting the pages.
Without a stiff cover that you can rubber-band the cut pages to, those pages are more likely to bend and get in your way. This is why paperback books are harder to make.
Ignore Step 9: Break the spine instead of cutting the binding.
You shouldn't cut the binding in Step 9 (obviously), but instead you can break the spine to get the cut pages out of the way.
During Step 11: Don't cut the back cover.
Fold it out of the way or put some thick material between it and the pages.
During Step 23: Put something flat on top while it dries.
After you glue it, make sure there's something flat on top of the book before you pile the weight on. Without the stiff covers, you need something else to keep the paper from warping due to the wet glue. In the picture to the left, I used another hardcover book for a flat surface and then a bucket of rocks for weight.
After Step 23: Let it dry for several days, if possible.
The glue will warp the book, but the longer it dries under pressure, the better it will look when it's done. The book on top was taken out from under the weight after 24 hours, while the one on the bottom sat there for 3 days.
Note: the glue will still warp the back cover, no matter how long you leave it to dry.
Note: I highly recommend that you use the Nail Method for doing paperback books. It makes things much easier, you don't have to break the spine to keep the cavity walls straight, AND it guarantees that you can't accidentally cut through the back cover.