The biggest problem I've encountered with the whole e-book thing is that it's such a good idea that virtually everybody is on to it.
The market is glutted with tons of self-published technical e-books. About 30% are good. The remaining 70% are pitiful and have had the unfortunate effect of damaging the reputation of the entire tech e-book market.
So unless you can interest a publisher (Que, O'Reilly, SAMS, Wrox, Prentice-Hall, APress, etc.) to sign you on, it's going to be a tough sell to the consumer since they don't know you. And getting the big publishers to take you on for an e-book is no easier than convincing them to put you in print, since they have their own reputations to consider.
The other big problem is "ad hoc reproduction" (i.e. bootleg) issues. Since an e-book can be readily duplicated and distributed without paying the author, the only way to really make out with an e-book is to use it as a marketing tool to help sell your other products or services.
Writing a good tech book goes a long way towards establishing your credibility and expertise on a subject. Ideally it will lead to additional publishing deals, consulting contracts, speaking engagements, or the opportunity to do a sales presentation. But by itself, it's usually little more than a lot of work for very little in return.
Smart musical groups have already started to realize they're not likely to continue raking in millions on old-style recording contracts alone. The smarter groups have already taken action by pushing their live performances, ancillary merchandise, and building their fan clubs - some of which charge a fee to belong to!
The fact that many fans are willing to pay for VIP memberships indicates these "clubs" are providing something more than a list of concert dates and a gallery of band photos. (Hint: priority notifications and announcements, advance private ticket sales, "preferred" concert seating, discounts on merchandise, "members only" unreleased singles, the opportunity to 'vote' on future concert locations, etc.)
So again, an e-book may work. But it won't be enough by itself. Most likely it will only be part of a larger suite of products and services that make up the rest of your revenue model.