I'm still palpitating at the number of DWJ novels which appeared in the fantastic AIBU fictional parents thread. (For those not yet in the know she was one of the best children's fantasy novelists of the last 40 years...)
The first one I read was 8 Days of Luke (showing my age...) and I loved Charmed Life and The Ogre Downstairs as a child, and was thrilled by The Time of the Ghost and Fire and Hemlock as a teen.
Then, in my 20s, realised to my delight that she was still turning out a fine book a year, so collected all those too!
I know there are a few other obsessive fans out there... please come and share. Which is your favourite?