Did you see this thread?
http://typophile.com/node/54817

How about TheSans Mono: http://www.fontshop.com/fonts/singles/lucasfonts/thesans_mono/

Fedra maybe?

I would like to release one too but it will be a few years at the soonest.

BTW what is the motivation for the mono or semi-mono?

What about FF Letter Gothic Text?

FF Magda Clean and FF Magda Clean Mono is another couple with real and "semi" monospaced styles.

I did see the other thread, just wanted to avoid hijacking it. I'm thinking of doing ascii artwork to illustrate the text and match them, hopefully using the same typeface.I'm hoping to find something along the lines of those multi-width typewriters, maybe three or four widths.

Maybe I should look for a monospace typewriter and do some custom editing of wide and narrow glyphs. I want it to be read, but still keep the mono feel somehow.

I'm not too keen on neither Letter Gothic nor The Sans. Magda is way too techy.

Did this quick sketch up to better explain what I'm looking for.

Looks nice! You image has a soft feeling and a little bit of a euro feeling as well I think.

Thanks Eben. Do you think something along those lines (in terms of character widths) could work in a book? Obviously not optimally.