Have a look at John Sans Condensed. It has a wide range of weights, has all diacritics on board and quite a soft look, especially in the lowercase.

H&FJ's Knockout has a ton of condensed/compressed cuts.
Come to think of it, their recent Tungsten might also be worth a look.

Trilon Condensed
Trilon Compressed
ClearviewText Condensed
ClearviewText Compressed

All have small caps and other OT goodies

Have a look at the condensed styles of Cyrus Highsmith's Antenna. They have a fresh look, and the angularity of Highsmith's style seems to work particularly well in condensed styles.

I was very impressed with how well the different weights and styles of Benton Sans worked together in Armin Vit's catalog for this year's TypeCon. This design was worked on first by Tobias Frere-Jones and then Highsmith. It is originally based on Trade Gothic, but worth a look.

Actually, Bill, the Benton Gothic/Benton Sans series was based more on Morris Fuller Benton's various sans serif series for ATF (including News Gothic, Franklin Gothic, and Lightline Gothic); hence the name.

Trade Gothic was Jackson Burke's variation on the theme, designed for Linotype a couple decades after Benton's.

Whoops, I mixed up Trade Gothic and News Gothic. Thanks for the correction.

I love Bureau Grot

http://www.fontbureau.com/fonts/BureauGrot

and think it's optimal for book cover design

I like Agilita.

Leo