This is probably the biggest draw away from e-readers for me and the reason I gave up on them.
For prose, Amazon's Kindle achieved the right form factor, battery life, display combo many iterations ago for me; but I seemingly can't handle having so much information available with a button press. It's just too little effort.
It's one of those oddities of being human, I feel. It seems perfectly possible in theory to learn about a complex field fairly rapidly by simply using Wikipedia and Google, but in practice the discipline required to not wander off-topic I find impossible to manage.
The sort of semi-procrastination that occurs when you're still being productive (because you're still learning), but you realise that you've gone from studying waveforms to ventricular fibrillation.
The thing that's so strange about it to me is that books themselves are alien concepts, there's nothing inherent about them - humans chugged along for millenia without them. Yet somehow, clicking off of an e-book for 'just a few seconds' to look something up seems to function differently to, say, closing one book and opening another.
Reminds me of the Doorway Effect.