6 books from the "Magic Tree House" series written by Mary Pope Osborne:

"#1: Dinosaurs Before Dark"  Year: 1992  -Published by Random House.  
Pages 1-4 are creased.  In good condition.

"#15: Vikings Ships at Sunrise" x2  Year: 1999  -Published by Scholastic.  
Wear to the binding.  In good condition.

"#17: Tonight on the Titanic"  -Published by Scholastic.  
Scribbling on the back of the first end page.  In good condition.

"#23: Twister on Tuesday"  -Published by Scholastic.  
Creasing on the back cover and wear to the binding.  In acceptable condition.

"#24: Earthquake in the Early Morning"  Year: 2001  -Published by Random House.
Big crease on the front cover and sticker residue on the back cover.  In acceptable condition.