His Master's Voice is definitely one of Stanislaw Lem's tougher, deeply philosophical books but nonetheless it's still a nourishing read. A mathematician is asked to join an elite group of braniacs gathered in a secret desert enclave to decipher an impossibly complex alien signal. What follows is 200 pages of dense deliberation, discussion and theorising about the nature of first contact, imaginings about alien motivations, possible civilisations, our own perceptual filterings scientific and otherwise and the preening short sightedness of the military/industrial complex which governs and funds our scientific endeavours. There no hint of the lightness to be found in Lem's Tichy memoirs or Cyberiad but it's weighty, dialogue heavy pace means there's few other scifi books that can match Lem's virtuosity in delineating the problems surrounding other worldly communications, far surpassing his own similarly themed novels Solaris and Fiasco. Brilliant but not for Lem novices.
The Forever War by Joe Haldeman is a brilliant militaristic scifi novel about a far flung war with an enigmatic alien race that's fought by soldiers whose deep space tours mean their eventual return to earth is centuries in the future. Haldeman's vision, clearly designed to echo his own experiences in the Vietnam conflict, nonetheless portrays the idiocy of all wars and nicely handles the indoctrination of draftees, the cold military machine and the agonising waiting before the inevitable bursts of combat. The protagonist William Mandella is involved in the initial phase of the conflict but after a troubled period back on a debilitated, war worn Earth where life, language and society are vastly different he returns to the conflict an officer and leads a squadron in a number of crucial encounters. Haldeman keeps things rocking along and packs in plenty of ideas and though the characters are a little underwritten it's still a classic of 70's scifi.