I have been buying ebooks for libraries since 2003, long before the current popularity of Amazon's Kindle or the iPad. Initially, the main barrier was availability of titles: the titles that you really wanted to buy were not available for purchase online. However, in the past couple of years this has been addressed, and many more titles are available. Although not yet everything, or even the majority of titles are available for libraries to buy.
With increasing availability, the main barrier has been usability - the ebook experience could be frustrating. Why, one thought, can't users download a chapter, as they would download a journal article?. This barrier is now being addressed by some providers. For example, the following books from Elevier and Wiley do allow you to download chapters, and you can read these on your ipad and/or Kindle.
The Manual of Photography (Tenth Edition)
The Art and Science of HDR Imaging
Platforms such as dawsonera and netlibrary will presumably have to adapt their offer, and there is some evidence of this happening. Dawsonera (our main supplier of ebooks), for example, have increased their printing limits, so at least in most cases you can print a whole chapter if reading on the screen is not for you, while Netlibrary have moved to a new interface.
To find out what is available, use Library Search to find resources on a particular topic and select 'Full Text Online' from the menu on the left. If you have any problems accessing ebooks or questions, please do get in touch.