The actual Frank and Nancy of this book is terrible but it features the rarest of rare things, NANCY JEALOUSY. Just going to quote my favorite bit because it's delicious:
"Quit it, Drew, she thought. Frank Hardy can like any girl he wants. Even though Nancy had a boyfriend--Ned Nickerson--back in River Heights, she couldn't help wishing then that Frank would pay more attention to her and less to Soong."
Pretty decent mystery by standards of the series, too.
AND NOW WE GET TO THE WHOLE POINT OF THIS MULTI-YEAR REREAD PROCESS: SECRETS OF THE NILE, BABY!!!!