To be honest I haven't read many of the novels on the list, but I voted for Gentle Cage since the plot's well though out and portrayed with enough realism to be just about convincing. Very very sweet.
Considering Ai no Kusabi's cult status, it's pretty much a must-read. Kinda hard-core tho. And tragic, oh yes. Wish June'd print the new Japanese edition illustrated by Nagato Saichi... And did I mention tragic?
Body Language, Don't Worry Mama, Like a Love Comedy and to a lesser extent The Man Who Doesn't Take His Clothes Off (in about that order) had me laughing mostly from the ridiculous set-up. Was it supposed to funny? I don't know, but you should probably avoid!! Selfish Demon King was a good kind of funny, however. Though I do wonder when they'll get round to translating v2.
I like it but on the whole I was disappointed by Only the Ring Finger Knows. It's a sentimental kind of story, but there were small parts in the translation that I felt didn't carry well and the book layout itself was annoying at times (namely v3!) I mean, I know the paragraphs in Japanese are one sentence, but there was no need to have the indents and margins so large they took up one line + one word = two lines! The page was seriously half-empty at times... And after such a good build up in v4, v5 was a bit of a let down even if it was a very romantic finish that tied in well with v1.
I haven't read Desire, Gravitation or Passion but you'd probably get a feel for the story from reading the manga.
Anyway I do recommend Love Water by Tachibana Venio and the Cold trilogy by Konohara Narise, which are both excellent stories. The illustrations are pretty too~
For people interested in non-translated books there are the epic Fujimi Orchestra (ongoing!) and Mirage of Blaze series. I feel the Mirage of Blaze Kaikou-hen Mashiroki Zankyou prequels might be more interesting partly because they don't deal with 400 years worth of emotional baggage... That, and the interaction between the Yasha-shuu members before they've properly bonded is downright hilarious...
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...Woah, that's a lot of writing...
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Hope it helps!