Much love for everything that Ligeti wrote. Most important artist of the 20th c. imo. And you're right, he had distinct phases throught his career, one that extends from the late 50's/early 60's up to 77/8 with Le Grand Macabre, a period of relative silence, and then another phase from the horn trio to perhaps the end of his life, although yes, sippal, dobbal, nádihegedűvel could have marked the beginning of something new had he been able to still write throughout the last years of his life. I recommend a french documentary on YT about him, if you're interested, it shows that he wasn't only a very fine composer, but also a very interesting man.
He was a modern composer who rejected dogma and schools and had perhaps one the most open ears (in the sense of open to all sorts of musics) ever.
EDIT: Of course, there's early Ligeti before leaving Hungary. From the 40's he had some very nice and short piano pieces, but his most outstanding works from that period are the Musica Ricercata, the Cello Sonata and the first String Quartet