When something is titillating, it makes you feel thrilled or excited. For your book report, your English teacher will probably make you read a serious novel rather than a titillating romance.
The adjective titillating implies a certain cheap or fleeting kind of excitement. Titillating things are unimportant and entertaining—maybe even a little bit lewd. The word comes from the Latin word titillationem, "a tickling," and its root titillare, " to tickle," which imitates the sound of giggling.