Free summer reading! NSTA Publishing usually offers a free pdf of one chapter per book. Here is a great book that is completely free. Yes- you have to download each chapter separately but it is a small price to pay. I highly recommend Chapter 1 by Mark Windchitl of the University of Washington- It will change the way you think about high school science instruction.
Click on the link HERE and then click on the CONTENTS tab half way down the page to access the pdfs.