Greeven discusses many very minor variants. It is therefore surprising that he does not discuss many other (in my opinion) important variants. One immediately misses the Endings of Mark. It is not clear why he chose exactly those readings and not others. Possibly there is a simple explanation, but it is not given.
Therefore the disadvantage of the book is that it is NOT a full textual commentary on Mk, because too many important variants are missing. It is Greeven's idiosyncratic selection of variants. Perhaps nobody knows anymore what the criteria were, because Greeven is dead now and the work has been published posthumously.
I suggest that in a second edition Güting should take it upon himself to add a discussion of at least the most important missing variants, to make the book more complete.
Just as some examples, the following important variants are not represented in the book:
1:2 in the prophet Isaiah / in the prophets
2:22 ALLA OINON NEON EIS ASKOUS KAINOUS +/- BLHTEON and omission by D, it.
5:1 GERASHNWN / GADARHNWN / GERGESHNWN
6:20 HPOREI / EPOIEI
6:45 EIS TO PERAN PROS BHQSAIDAN
6:51 they were amazed in themselves, and were wondering
7:14 PALIN / PANTA
8:35 "for my sake"
9:24 META DAKRUWN
9:43 – 48 SKWLHX / GEENNAN TOU PUROS: of all these only verse 47 is covered. Belong together.
9:49 "For everyone will be salted with fire."
11:3 KAI EUQUS AUTON APOSTELLEI PALIN WDE
11:26 omit verse
14:24 THS KAINHS DIAQHKHS
14:41 APECEI TO TELOS
15:28 omit verse
15:34 "why have you forsaken / reproached me?"
16:8 ff. The endings of Mk
Greeven normally does not discuss Western-only variants.
Wieland Willker, Bremen, Germany