I like having tech books around as reference and for ideas (Ruby, Python, Linux, security, style, …). I tried various books apps to use them: bad idea – no way to leaf through them easily on ereaders, although desktop isn’t too bad. I tried hardcopy which is better but bulky. The real problem is obsolescence. Both of the forms are subject to that.
I was a big user of Lynda, but video is just too damn slow to pick up on essentials, and it is also horrible for browsing, and it’s gone into the trashcan since LinkedIn bought it.
I’m now trying oreilly.com. They might have gotten this right. One subscription, no purchases, a boatload of resources. It still has the browsing problem, but I can use the desktop for that, and they add newer titles regularly. It’s not cheap though.