This Supraphon 3-CD box set (fat-box jewel case) contains superb performances of Martinu's seven string quartets recorded between 1979 and 1982 in excellently engineered analogue sound. The Panocha Quartet members, at the time of these recordings, were Jiri Panocha (1st violin), Pavel Zejfart (2nd violin), Miroslav Sehnoutka (viola), ans Jaroslav Kulhan (cello).
Martinu's quartets were composed right through his career, from the first, clearly influenced by Debussy and Ravel, in 1918 to the seventh in 1947. I think all of the quartets are of the highest quality, absolute masterpieces of the literature, and so few people seem to know them at all, which is such a pity. The quartets have been lucky on disc, and whilst I am very happy with this Supraphon set, the recordings on Naxos by the Martinu Quartet desrve a hearing, too (
Martinu: String Quartets Volume 1, for example).
These are not "thorny" works, but I would suggest that the sunny fourth quartet from 1937 might be a good place to start.
Unmissable!