I have used The Great Horologion (Holy Transfiguration), The Horologion (St. Tikhons) and The Hours of Prayer (ACROD), but haven't found any one to be so far superior that I would recommend a specific version and dismiss the others. I'd say that it probably depends on how much money you want to spend. For the ones I gave, the prices would be something like $90, $55, and $10 respectively. Obviously the more money you are spending, the more information you are getting. Then again, like someone said, to really, really, really do things "right" you'd be spending a month's wages anyway. If you're just Joe Layman and are trying to incorporate some extra prayers into your daily prayer cycle, then IMO there's nothing wrong with the $10 version. If anything, it's better, as you won't have to hold a 5 lb. book in your hands for all those lengthy prayers.