My son is 12 and has always been such an avid reader, he's won his school's "Scholastic Reading Counts" award every year. My answer will be based on his opinions, and my reading of his books, too.
I agree with YOU that Captain Underpants is lowbrow, and also appeals to encourage a bad attitude.
My best suggestion may sound bizarre at first, but I noticed that after my son read them, he had a little better appreciation for subtle humor and pathos, found often amid tragedy..and that is the entire Series of Unfortunate Events. They are about one tragedy leading into another for some very unfortunate children, but embedded within the story of their lives, absurd humor is found, as is sometimes the case in real tragic lives. The author of these books is the child of Holocaust survivors, and I suspect that the ability to find humor amid tragedy comes from that paradigm.
These books were also very popular with most of my son's friends. The Redwall books by Brian Jacques, despite their being about cute little forest creatures, are books filled with epic tales of conquest, deliverance from slavery and imprisonment and are more intense than many parents realize. They take place over several generations and I enjoyed reading them, too. They are also extremely favored by the boys and when my son was 10 and 11 were his absolute favorite books. He even liked these better than the Harry Potter books.
One book my son enjoyed last year was the book based on the Television show Myth Busters. He learned interesting things and it interjects humor to make the book even more entertaining than a television episode.
Other books that he enjoyed, not so much humor based, but of interest to boys, include the Artemis Fowl series of books and of course the Tolkein classics..the Lord of the Rings Trilogy and the Hobbit. Age 10 appears to be the time when many boys start showing interest in those books.
I briefly mentioned Harry Potter..I loved those books, and so do most boys.
For Hanukkah...and humor..a good one is Herschel and the Hanukkah Goblins.
Island of the Blue Dolphins mentioned above was MY favorite book as a child, but it isn't so much humor as about a wonderful story of a woman's struggle for survival, based on a true story.
Last, for Jewish children there is a great book by one of the most famous of Jewish authors, Scholem Aleichem, quite appropriately titled, Jewish Children. It really isn't for very young children and age 10 is perhaps old enough to understand the humor and also deal with the tragedy, while learning about the world of the shtetl of the 1800s...
Shalom :)