The Library has just purchased 412 SPIE ebooks that were published between 1989-2020. The ebooks include monographs, tutorials and field guides. All of the ebooks are available from SPIE's Digital Library. Use this proxied link to navigate to the SPIE ebook site -
https://clsproxy.library.caltech.edu/login?url=https://www.spiedigitallibrary.org/ebooks?SSO=1
And then browse by subjects such as lasers, medical imaging, biomedical optics, remote sensing, medical imaging, nanotechnology, solar energy, astronomy ++
Some sample titles are below and include proxied links.