Charles Darwin’s Library is a digital edition of the books comprising Darwin's personal library.
From the site's History & Scope section:
. . . . the library of Charles Darwin is more than the collection of the works he owned at his death. As Francis already appreciated in 1908, ‘The chief interest of the Darwin books lies in the pencil notes scribbled on their pages, or written on scraps of paper and pinned to the last page.’2 Darwin did read both systematically and with great intensity. He read to gather evidence, to explore and define the research possibilities of his evolutionary ideas, and to gauge reactions to his own publications. In fact, reading was a major tool in Darwin’s scientific practice. Thus what our digital reconstruction of the Darwin Library delivers is the ability to retrace and reduplicate Darwin’s reading of a wealth of materials.Also useful to the student of Darwin is another open access site: The Complete Work of Charles Darwin Online.
The portion of the Darwin Library now published at the Biodiversity Heritage Library constitutes Phase 1 of a collaborative project to digitise the Darwin Library works and to provide transcriptions of Darwin’s marginalia side by side with the pages he marked. Phase 1 presents images and marginalia for 330 books, represents 22% of the total 1480 Darwin Library book titles. But, more significantly, these 330 titles represent 44% of the 743 Darwin books that bear his annotations or marks. The latter comprise 28951 annotated and marked book pages and 1624 attached note slips. Plans for further phases to complete digital publication of the remainder of the Darwin Library are now under consideration.