I am a bibliophile - I love books and especially American Humor.
The book you desire depends upon your needs:
(I've just finished reading a fun 10 volumn set of American Humor published 1907)
My best advice, is to go to a store for used books and browse, and browse and browse - There are dozens of collections of American folk humor/lore. Before you fork over 60 to 120 dollars, browse your local university library.
Try these: The Frank C. Brown Collection of North Carolina Folklore
Another suggestion is something you DO NOT give to a kid - THE ANTHOLOGY OF CHILDREN'S LITERATURE - 1100+ pages.... My copy is 1947 and is noteworthy because of the addition of its new section, "Folklore That Has Inspired Good Music." There have been six or seven other edtions, the older are better for folklore.
Collected by high school students - THE FOXFIRE SERIES - for a modern collection of Appalacian Folk Tales and Crafts (older 1970's are better)
The WPA Writer's Project Books from the 1930's - Collections By State and genre
The four volumne Vance Randolph series gives you folksongs and a lot of lore to go with them.
For a good "on-line" resource you cannot beat the Library of Congress collection of American Folk Lore at http://www.loc.gov/folklife/other.html
WORK HARD, HAVE FUN, LAUGH A LOT
Sincerely,
Gargoyle