The Mammoth Book of Extreme Science Fiction

First of all, it's ordinary scifi, not extreme. Good scifi, not bad (except some stories) but... nothing extreme here.
Second, out of 19 stories, I found only 5 to be 5/5s, with just 2 really memorable: Alastair Reynold's “Merlin Gun” (good story with amazing ending of galactic implications that caught me into a loop of “What should be done?”) and Harlan Ellison's “The Region Between” (a great mix of different blends of scifi and an extremely original form). I also found stories I just couldn't finish (Doctorow, Cadigan, McDonald), not that good (Baxter, Gillet, Kelly) or really bad (Oltion's “Stuffing”), with plenty of middle-range (average) others.
The average is 3,5/5, but as a whole I felt the anthology is a 3/5. Not that bad, not that good.