The London based publisher, BookBoon has been offering free guide books, technical books and textbooks for the last seven years. Instead of charging readers for textbooks, BookBoon instead sells advertising in the downloaded eBooks. The average book contains 6-9 half page ads. They have set new records in eBook downloads with 11-million last year.
The publisher currently offers well over 1000-titles, in 6 languages. Any books downloaded are DRM-free PDFs.