To view the fort details you first need to have Google earth on your computer.
If you do not have good earth you can download google earth http://earth.google.com/index.html
After you download and install google earth you can download the attachment Forts in Maharashtra.kmz, to your desktop and double click on it and it will install all the points in google earth.or you can download individual points from here
you can read these sahyadri books online free .But they do not have the maps and other features for which you would need too buy them and they are at a very nominal rate most are less than 200 Rupess (Price less than one trek).
http://www.mumbaihikers.org/2008/07/books-in-trekking-sahyadris.html
