Towelhead is another I didn't care for that much. It was a good enough read, but I found the writing to be rather average and the story not particularly special or eye-opening.

Sons and Lovers by DH Lawrence. Boring.
Jude the Obscure by Thomas Hardy. Same.
The Great Gatsby. Pointless reading.

I think Villette is pretty underrated since Jane Eyre is Charlotte Bronte's classic.
I know there are other books I've read that are underrated, but I can't come up with them.