BiodiversityHeritage Library - Books
http://www.biodiversitylibrary.org/

Directory of Open Access Books (DOAB)
http://doabooks.org/doab?uiLanguage=en

Gallica
http://gallica.bnf.fr/

InTechOpen
http://www.intechopen.com/

T.C. Kültür ve Turizm Bakanlığı e-Kitapları
http://ekitap.kulturturizm.gov.tr/site-agaci

NCBI (National Center forBiotechnology Information) - Books
https://www.ncbi.nlm.nih.gov/books/