THIS WAS SOOOOO DELIGHTFUL THAT I BASICALLY READ IT IN ONE SITTING. Diana Wynne Jones has such an unparalleled, wickedly fun imagination - I don't think I've had such a good time reading fantasy in years. I genuinely got emotional at the sibling stuff at the end too (the characters were so unique and it was just SO SWEET!!!!) 
 READ THIS BOOK IF YOU LOVE DYSFUNCTIONAL WIZARD FAMILIES, WEIRD PRECOCIOUS KIDS, TIME PORTALS, SEEMINGLY BORING TOWNS WITH REALITY-BENDING SECRET POCKETS AND VERY ENGLISH, VERY EXASPERATED CHARACTERS.