What Part of No" (Don't You Understand)" is the penultimate part of the series of books that began eleven books ago with "The Magic Apostrophe." Tan'ith, Lady of Ynys Haf, is planning a family, and she really needs maternity cover... Unfortunately her magical teenage niece Cariad is not impressed by the idea. Whilst this book is a continuation of a series, it can be read as a stand-alone leading into the final part, "Tree of Light."