It's not an exhaustive source , but most of the books on most of the relevant technologies can be found.
To download a book, just click on the detailed book information section and you would be redirected to the download page. You need to answer a security captcha before the download can begin.
The books that are downloaded through the app are strictly meant for private, individual reading and for only for informative purposes.
On some versions of android, there is a problem opening the downloaded PDF file. Please have a PDF reader installed (such as one from Adobe) for viewing the downloaded books.
The app makes use the http://it-ebooks.info/ API. The books are served from filepi.com. One needs to answer a security CAPTCHA before the actual downloading of a file can begin.