There are loads of guides for making book safes on the internet and all the ones I looked at are pretty similar. The main ingredient is a book thick enough to hide your stuff.
I had pretty specific requirements; I wanted to be able to store a drinks measure and a small bottle, so I went for my six novel James Bond anthology (when I did @bondsbooze I bought them all individually so I don’t feel any guilt about gluing the pages together and hacking a big hole through them).
We went away for the week recently and I was able to squirrel the measure and a bottle full of sugar syrup into our luggage, but I could have easily snuck a couple of miniatures in there. I think Q would approve.