How to publish an academic book but make the PDF freely available online? Background

I like the idea of writing an academic book.


It currently looks better on a CV when applying for jobs, grants, promotions, etc. than a blog post, or a website.
Libraries and people archive the work
Most of the best academic content currently seems to end up in books and journal articles, rather than on websites.
People have an attractive physical copy to engage with if they want.


However, I don't like the constraints imposed by a book. In particular, readership is limited to those who buy/borrow the book or have access to a library.

Aim

In some cases, I'd prefer to write something like an "open access book". 


If readers want the physical copy, they can purchase the book. Ideally some of this revenue would go to the author, but I'm not too fussed if the publisher just uses this money to fund promotion, editorial assistance, production, etc.
However, access to a PDF of the book is free online. 
The book gets an ISBN, archiving, availability on Amazon, etc. and all the academic recognition associated with publishing an academic book.


Questions


So, are there any options for doing this, and what might be best option?
Are there any case studies of others who have done this?
Cambridge University Press allows authors to freely distribute electronic copies of the books that it publishes, at least in mathematics and computer science.  (Of course this has to be explicitly negotiated into the publishing contract.)  Two good examples are Allen Hatcher's Algebraic Topology and Steve LaValle's Planning Algorithms.

You could also just release the book on the web, let people create their own physical copies through a book-printing service like Lulu or Blurb, and rely on the quality of the text to bolster your reputation instead of a traditional publisher's imprimatur.  See, for example, Pat Morin's excellent Open Data Structures.  However, I don't recommend this route unless (a) you write an amazingly good book, and (b) you already have tenure.