I enjoyed reading the other reviews here but I wonder if people unfamiliar with the work might be misled by the constant reference to dreamscapes. A dream doesn't only mean the alternate reality that appears when we sleep. Sometimes to "dream of something" implies that you long for it to come true in reality. Just as importantly, the opera also revolves around memory or the lack thereof. You can only dream of something if you can remember it clearly. The most vivid memories are often from childhood and these often play a large role in what we dream of while awake. Sometimes a place that one hasn't seen for a long time changes so much that there is bitter disappointment that the people no longer remember them and their own memory no longer matches what they see.
The action or plot doesn't have the outright bizarreness of an actual dream or nightmare. It's more the dislocated unreal feeling one might have if most but not all memory was clouded or absent for no apparent reason. The setting is fairly prosaic: a salesman Michel returns to a seaside village on a sentimental visit to locate a beautiful woman he heard singing from a window. But the townspeople have trouble remembering clearly anything about their own town such as where a hotel is. Michel's memory starts to get vague along with the townfolk. One of the villagers tries to abduct Michel so that Michel can provide him with childhood memories. The villager wants Michel or anyone else who has any childhood memories to relate them to him so he can have some to call his own. The fact that the childhood memories are someone else's is immaterial to filling that terrible void. Eventually Michel does find that beautiful woman who is named Julietta or at least thinks he does and various complications follow. I hope this provides a bit clearer idea of the basic story Martinu was setting.
As other reviewers have noted, the opera contains some of Martinu's most inspired music. The opening has a high bassoon wailing away in a manner totally different that the opening of Stravinsky's Rite of Spring. This segues into the arrival of Michel at the village where someone plays an accordion and you are soon drifting through a series of nominally realistic but slightly disturbing interactions between the characters who have trouble remembering things in the most awkward circumstances. The music captures this mood perfectly with its varied scoring that is always sliding in different directions without being harsh or chaotic. The musical performance and singing are idiomatic and emotionally committed.
The recording as noted in other reviews does have a slightly hard treble and a bit of light graininess. Unfortunately for modern listeners the monaural version of the LP recording was a bit better than the stereo version now the basis of CD transfers. Quite frankly digital transfers rarely make an LP with slightly ragged treble any sweeter, usually they make it worse. It is not to the level of annoyance however. I would recommend those with turntables to seek out the original LPs whether stereo or mono.