I'm going to go ahead and recommend the entire Vorkosigan saga, by Lois McMaster Bujold. I advise reading in chronological timeline order (except for the prequel "Falling Free" which only loosely bears on the rest of the series's events and characters - so start with Shards of Honor). Before I read these books I had heard HPMoR glossed as "Miles Vorkosigan attends Hogwarts", and while this does neither character perfect justice, it was a lot truer than I anticipated.