I understand that you can't change the resolution, but when I'm playing on my 27" monitor the game is either too small (don't change desktop resolution) or it stretches the image (change desktop resolution) so it's even uglier than it's supposed to be.

Is there a way to play this without it stretching the image while actually able to see what's going on?

NOPE

Sure there is, just change your resolution to another 16:9 (if that's what you have) one beforehand.

So if you are using 1920x1080 normally, you could try changing it to 1600x900 or even 1366x768.
It will not be as sharp as the native resolution but it won't be stretched.

Check the table here: http://en.wikipedia.org/wiki/Display_resolution#Computer_monitors

EDIT: Hmm, maybe this doesn't work. At least the mac version doesn't ask me whether or not to change resolution, it always does… But if you get a dialog and you have the option not to change the resolution then it should work.

Alright, tested this quickly, and it does seem to work. A bit of a chore but at least it's possible to play this. Thanks.

I'm playing on 1440x900 in a window, and the game isn't too small for me. But I understand it may get too small in higher res, especially because the game screen takes like 1/4 of the entire window :D

I haven't tested if this actually works, but if you have Windows Vista or later *and* your native screen resolution is at least twice as large as the game resolution (in each direction, not in terms of total pixel count), then the Windows Magnifier might offer a good alternative.

Launch the game, and don't let it change the resolution. Then, press Win-Plus to launch the magnifier. Assuming you haven't touched the default settings, this should make everything render at 200% of normal size (so there will be no scaling artifacts).

Minimize the Magnifier window or move it somewhere where it won't bother you, then play the game.

When you need to zoom back out, hit Win-Escape to close the magnifier and restore normal zoom. If it's just for a brief moment, then you can also press Win-Minus to zoom out temporarily, and then Win-Plus again to zoom back in (which should be a tiny bit faster).

I think Avernum 1-3 use 800x600, so if that's correct, you'd need a 1600x1200 screen (or larger) to fit everything. If your screen is smaller than that, this will still work, but you won't be able to see the entire game at the same time, and you'll have to move the mouse near the edges in order to scroll.