While the Shivers book series is the more popular body of work by M.D. Spenser, the quality of the Humano Morph series is just as high.
The books are about a group of students who, through a mishap with some chemicals, are now able to morph into other humans simply by thinking about them. Obviously, this helps them work their way through the adventures that life throws at them.
If you can find these books, I highly recommend them.
#1: The Secret of Bearhead Holler
#2: Deep Trouble at Dolphin Bay
#3: Caution: The Contents of this Book may be Hazardous to the World
#4: Air Morph One: Ready for Takeoff
#5: Blasting into the Past
#6: What would we do without Jill?
There were six books total in the series.