One of those minor iTunes mysteries

If I'm listening to a podcast and I have to close iTunes, the next time I open iTunes, it remembers where I was in the podcast without my having to grope for the spot.

But the same isn't true if I'm listening to an audiobook. iTunes opens to the right playlist, but it doesn't have any sort of bookmark feature to remember where I left off -- I always have to go hunting for it.

Any idea why the difference -- or if there's any way to fix this? It's tempting to set the current book in progress as a podcast, just for this feature.