Any book that the first born asks to read again immediately after finishing it is going to be well treasured in our house.
The Notebook of Doom series from Troy Cummings is wonderful. Quick to read, full of fun, adventure and silly drawings and characters that make the kiddo laugh.
For adults reading it to the wee ones, most chapter titles are puns so glorious they should be studied in English classrooms. They read in less than an hour and honestly I wanted to keep reading it too.
The book encourages creative thinking and has a slew of post reading activity ideas on the back cover.
The firstborn has been running around acting out scenes and shouting “watch out for the balloon goons!” around every corner. Just tons of fun. Check it out here: http://www.amazon.com/The-Notebook-Doom-Balloon-Branches/dp/0545493234