Often typified by a combination of European sans-serif type with intriguing imagery, the ECM label has built an archive of influential sleeve design around its classical and jazz releases.
Sleeves of Desire - A Cover Story compiled many of the key moments from the back-catalogue including the abstract approach of Barbara Wojirsch. Anyway, I've routinely had the library copy at home and was beginning to think that I should get one for myself. Although now out of print, I was shocked to see that the best price I could get on a used copy was £200. So, basically, if you see one knocking about in a charity shop, snap it up. Then drop me a line and I'll give you back the 20p that you paid for it.
Failing that, a more reasonably priced alternative that focuses on ECM's output is more widely avaible. Granta's Horizons Touched - The Music of ECM can be ordered via ECM's site for €29 [link above]. Meanwhile Lars Müller Publishers (the company that printed Sleeves of Desire) has issued Windfall Light - The Visual Language of ECM which places considerably more focus on some of the photography-based artwork.
That one is currently discounted at Amazon via the following link:
Windfall Light: The Visual Language of ECM