It would be hard to pick one "best" illustration job after all these years. But my Great Thistledown Flood comes to mind because it was the first kids' book that I wrote and illustrated, and I was honored to have it voted a Gold Medallion Honor Book at the CBA Convention. That book was day and night seven days a week for five months. I remember getting a call from a school principal one night...he told me that his daughter read to him for the first time that day...from my Thistledown book. And another call from California late one night...someone couldn't find the ladybug that I hid on a page from Thistledown, and she was deeply distressed.
And the Where's Dan Quayle? and Where's Charles and Di? books were an unforgettable memory. Because they sold into the hundreds of thousands I was getting constant calls from newspapers and radio stations all over the country for interviews, and featured in People Magazine, Time, Newsweek, USA Today and many other major mags. I was even booked onto David Letterman because of the Dan Quayle book (but they canceled out the day I was supposed to leave for New York because they thought the book might stir up too much controversy). So it was exciting, but again both books were day and night seven days a week for five months, and allowed me to attend the ABA Convention at the publisher's expense.
Sigh...it seems this day and night job never gets any easier. Now Mrs. Trowbridge is the cruel task mistress.