Free textbooks

Fifteen sites and counting... 
offering tens of thousands of free textbooks to make you more brilliant than Einstein.
Resource: Thousands of free educational books to download in pdf format. No registration required
Resource: Search and download a particular title for free or browse hundreds of free titles available by subject.
Grade Suitability: 7,8,9,10,11,12, AE
Resource: E Textbooks to download and print
The CK-12 Foundation is free service for learners and educators to download, print and use text books on core subjects. Funded by the Amar Foundation and Vinod & Neeru Khosla who believe that everyone deserves the opportunity to learn. The foundation is a non-profit with the aim of producing free and open-source K-12 materials aligned to state curriculum standards customised for students or teachers' needs. 
Grade Suitability:
6,7,8,9,10,11,12
Resource: Online textbooks.
Choose from a collection of ready-made "off-the-shelf" books or make up your own by selecting relevant subject matter. 
Grade Suitability:
6,7,8,9,10,11,12
Resource: The Elements of Style by William Strunk Jr. This classic reference book is a must-have for any student and conscientious writer. Intended for use in which the practice of composition is combined with the study of literature, it gives the principal requirements of plain English style and concentrates attention on the rules of usage and principles of composition most commonly violated. 
Grade Suitability:
4,5,6,7,8,9,10,11,12
Resource: Fun workbooks on creative writing in editable pdf format.
Grade Suitability:
k,1,2,3,4,5,6,7,8,9,10,11,12


Resource: The reading and literature list for the Robinson Home School Curriculum with links to online free downloads in pdf, kindle etc format. NB: The second link, the list sorted by Grade, is from a third party - not how the Robinson Curriculum orders the work.
Textkit provides these two Latin textbooks for download as well as Latin readers.


Grade Suitability: beginner to advanced
The Pilgrim's Progress from This World to That Which Is to Come is a  Christian allegory written by John Bunyan and published in February, 1678.  It is regarded as one of the most significant works of religious English literature. This is an illustrated edition
"Parallel Alternative Strategies for Students (PASS) volumes are unique, supplemental materials written to help students with various learning needs achieve success in the classroom. The student volumes are presented in an easy-to-understand format for students seeking a standard diploma. The information is written by the Curriculum Improvement Project team in a manner that offers more understanding in less time. "
Grade Suitability: 9,10,11,12
372 free textbooks on Art History from the Metropolitan Museum of Art. They can be read online or downloaded in pdf format.
Science Workbooks and Teachers Guides in either English or Afrikaans in downloadable pdf format.
Grade suitability: 4,5,6
Getty Publications virtual library gives access to hundreds of publications in the art and art conservation domain.
Grade suitability: 10,11,12, AE
Free  text book on American Government written by a former history teacher. The "laboratory of democracy."

Free text book on American History, with 60 chapters, from Pre Columbian to modern day.
Free text book on Ancient civilizations.