The Technotes from this site will be a great help. Although, not 100% updated for the new objectives, the vast mojority of the core knowledge is still the same, and the Technotes make it easy to understand.
Technotes and practice, try every single thing you read as far as you can so you will understand what is it about, that is the best you can do to study it just one time and get it right
Comments
I recommend the Techexam Notes and Passport Network+ book.
good luck!