Just got my newest toy - a 5 3/4' rolling ladder for the study. About a quarter of my shelf space is contained in the top two shelves, which require basically a six foot ladder to get to. Instead of getting a rolling ladder system which would prevent me from putting chairs in corners, and put a unsightly brass rail across the fireplace, I got a "pulpit" rolling stepladder from Putnam Rolling Ladder. It has four steps to a standing platform at 36" off the ground, with metal handrails, and a book platform in front (hence the name "pulpit") It rolls on four wheels but once you step on it it sits down on the floor, so it's plenty stable. And it's very easy to work from, since you can stack book on the pulpit and roll them around - no balancing on a stepladder with an armload of books.
Unfortunately, I couldn't get it in any wood but oak, so even though I stained it with the same red mahogany as the rest of the study last weekend (didn't trust the manufacturer to get it dark enough), it still look relatively zebra-striped compared to the cherry bookcases and paneling. I am putting rub-on polyurethane on the steps and platforms, but after spending a solid day last weekend staining this beast, I am not in the mood to steel wool and rub any more than I have to.
It is a big hit with the boys - Collin and Parker love to climb it to get books off the bookcases, and with the handrails, they can get up and down easily.