Marvel Digital Comics: http://www.marvel.com/digitalcomics

If you're looking for Classic Marvel comics and back issues, Marvel Digital Comics has a couple of thousand comics on their Digital Comics (online reading) service. 

Note: I'm unable to get past page 4 on any of their "free" comics, it prompts you to sign into/sign up for the service (*possibly* related to the "U.S or Other" question you're prompted to answer when you first hit the site - try selecting U.S, you may get past page 4 on free comics) but  my experience is that you're not getting past page 4 even on free comics.  Please let me know if you are able to.

In any case, from what I've seen, it's quite good. 

Page transitions are nice (an animation of the page turning) you can view by single page or double page layout with a zoom feature on either, and my personal favorite, the smart panel view mode (which does what Beamable did - auto-focuses and zooms a single panel at a time, you simply press your right arrow key to read a page in sequential panel order - ergo no need to fish about panning and zooming)

The $5 a month subscription fee (when you sign up for $60 a year) is not bad.

But I would have 2 suggs to make it worth my while.

1. I should prefer being able to auto-save the comics to my hard-drive. 

For 2 reasons.

a) so as I can keep issues on my HD and read them offline at my pleasure.

I try to avoid "temporary live renting" whenever possible, it tends to feel like ether-economics given that at the end of the day, you've spent money and own nothing tangible. 

id est. I prefer to buy a movie for $10-$20 at the video-rental-store than rent it for $6 new.

b) so as there is no need to constantly (re)-download pages on the fly, which appears to be the current model.  A time and PC resources consuming process.

2. Failing the former sugg, then including 2 NEW issues/comics (chosen by the subscriber preferably) would likely push me over into/justify the $5 a month subscription model.

Otherwise, I'd more likely be interested in a $5 a month NetFlix like NEW Comic service. Save in digital download form.

For Marvel's back-catalog and reading all those seminal Marvel comic-book story-arc's, the service is quite good; the online reader is excellent, imo the service just needs a little extra to justify the $5 monthly subscription fee.

It appears to be undergoing change, so it's one to keep an eye out on.

Judge for yourself 'ere: http://www.marvel.com/digitalcomics/

The Avante Guardian. ---- Einstein's Hair^2 //Approved.