Library Journal and School Library Journal have published a survey of eBooks in US libraries. The number of public libraries offering eBooks increased 10% this year to 82% of US public libraries. Academic libraries are at 95%, a 1% increase over last year.
Public libraries spent about 4% of their materials budget on ebooks this year, and predict that it will increase to 8% in the next five years. Given the pace of change, this estimate may be low. A chart from the article is below: