This topic came up a while back and I hadn't had chance to respond. In the meantime I found some pre-made books that can be used to hide valuables at Michaels arts and craft stores.
Here's a picture of my two books.
Death Beam, in the center is a book I picked up used for 50cent and carved out the inside. (I like the title.) I hollowed it out so that a PPK/s would fit inside. The book to the right of
Death Beam is the fake book I bought at Michaels for only a couple of bucks. They sell it to use to hold Christmas presents.

Here's how they look removed from the shelf

And here's what's inside. The XD is a little snug, but I just had it handy and put it inside for illustration purposes.

I know my "carving" is a little crude, but it was a proof of concept and I never went back to clean it up. I used it for a couple of years, but now I just carry my PPK/s rather than keep it on the shelf. Given some time, if anyone's interested, I've got another book that I intend on carving, I'll post a how-to with pictures, later.