Each book holds about 600 stamps, so as I get new stamps I can insert pages and reorder them. Using the movable page system, you can swap countries between books very easily. Even better is Hagner sheets, but they are a bit more expensive than the books I usually use, and not terribly versatile, e.g. you can't put a mini-sheet onto a normal page, the item must fit in the slot. I'm going completely to good stock books. Since everyone's approach to and attitude toward philatelic material varies, no album seems to fit the requirements of most of the collectors.
Some countries take an entire book, but letters 'D' and 'E' fit into one.
I'm interested in the various perf., tagging, precancel, and paper varieties. I hope that in time the Vario pages won't degrade my stamps.