I keep seeing what seem to be variations of this meme, but there are always different books on it... kind of randomly selected. Maybe people are adding and removing books as it's doing the rounds?

The Vorkosigan series reaches its fullest potential with Miles as the main character, I think, and personally I prefer the middle books of the series. Cordelia just feels like she's too much of an authorial mouthpiece at times. And Shards of Honor follows a much more conventional plot arc than most of the series.

Oh, Ender's Game. I loved the first book, from memory, but the subsequent books were... well, odd, and I didn't finish the series. Card really seems to toe the line in terms of letting his agendas swallow the story. Themes are good, but I prefer them not to be in the shape of anvils. :p