Before I move on to the philosophy of Ulrich Horstmann, another great german pessimistic thinker, I will answer some questions that have come up here, on facebook and other communities, and will go more into detail with some points about Mainländers philosophy I haven't pointed out yet:
"I have a problem with the GOD-part"
Some people seem to be detered by the word "god" so much that this word alone makes them question the entire philosophy of Mainländer. I guess what I didn't point out good enough in the "rotting god"-essay, is that Mainländer only uses the word "god" as another word for "singularity" or "basic unity" or however you want to call it. It is not an actual "god" and that god is also not actually committing suicide - you could also say: The singularity destroyed itself instead of "god committed suicide". So all in all: GOD is just a metaphysic symbol, to make the philosophy more poetic.
"I don't get how the will to die can be the driving force of a universe that created life"
Since entropy seems to be the driving force of the universe, it's actually possible. Like you can say "singularity" instead of "god", you can also say "entropy" instead of "will to die". If you keep the picture of the rotting body of god as our universe in mind for one moment, then all the unorganic individuals (gases, liquids, stones etc) are the dead body parts rotting into nothingness, while WE, living beings, are the maggots in the rotting body of God, which is the world. So yes, we are something special in some way, but we are just rotting to notingness in a different way than the rest of the dead body.
"If god wanted to kill himself, why couldn't he reach his goal, nothingness, immediately"
Mainländer states that the fact, that the world exists, is proof enough that the obstacle for god was his own existence, his essence. He couldn't turn into nothingness just like that, because he was in his way, his own essence was stopping him for leaving his existence without thereby creating a world, that has now to fulfill the will to die. Imagine, that we are not living, but dying all the time. life is just a dying process, but what is in the way of reaching the goal of death right now? Right, we are in the way ourself, our essence is the obstacle of reaching nothingness, which is the goal of every life, immediately. This is representing gods own obstacle before the world was created.
"How is Mainländer a pessimist/antinatalist when there is a meaning in his world"
That's right, in Mainländers world there is a meaning. The meaning however, is solely to die for everything and everyone. The antinatal part develops from his philosophy simply as a consequence, because why create more food for the slaughter machine? You can imagine Mainländers cosmos as a assembly line of death, and the movement of that assembly line is the only meaning there is to it all. All the things that are transported on the assembly line, like stones, plants, animals and humans are absoltely worthless and are only there to be chopped at the end of the line, to reach gods goal of nothingness.
"The ideal state is the absolute utopia. It's beyond pollyanna. How does that fit in"
It fits in perfectly, because it would theoretically be the ultimate goal of humanity, something that has been worked on since the first caves where lightened up by torches. It is, however, just an abstract thought, not something that will ever be reached in reality, at least it's very unlikely. But the ultimate goal of humanties movement would be that state and the only thing left to do after reaching it is indeed to end it all, because 1. life is still pointless and futile, even when it's perfect and 2. the movement of the universe can't be stopped, therefore a stagnation in the ideal state would not be possible for humanity, because it is part of the overall movement of the world.
Some information on the person Philipp Mainländer:
Mainländer was influenced very strong by Arthur Schopenhauer and his will-metaphysic and for someone who isn't familiar with Schopenhauers work, Mainländers "sequel" might seem complete nonsense. I can only suggest anyone who wants to read the actual book of the Philosophy of Reedemption to read Schopenhauers mainwork "The world as will and representation" before that.
Mainländer has also written some dramas, novels and poems. His death wish shines out of all of them here and there, however the creation of "the will to die" is of course the peak of this development. Mainländer joined the army several times, because he wanted to die at the battlefield on purpose to fulfill his death wish. Several attempts failed, before he got to write his 1.300 pages strong Philosophy of Redemption. After doing so, he used a pile of copies of his own books as a pedestal and hanged himself in his residence in Offenbach. He was 34 years old when he left the assembly line of death and entered the eternal kingdom of absolute nothingness.