On the first, I reacted pretty much the same as the other reviewers, dashing off a two-sentence synopsis to a friend and telling him not to bother.
On the second reading I began to appreciate it more though, although readable, it's actually less accessible than some of Moore's other works (the first two LOEG volumes for example). I can understand why other reviewers were disappointed because the League appears relatively ineffectual in the story which itself is very separate from the other plot strand until the very end. We expect our heroes to, if not always win, at least have a significant effect. Here they are misled and ineffective.
The other part of the story concerns what happens to Nemo's daughter in London's East End, and not very pretty it is either, told in the manner of Brecht's Threepenny Opera with her as Jenny Diver and Macheath as a returning Jack the Ripper.
Operas tend to have prologues and this LOEG volume is essentially the prologue to the new series. What happens here will resonate in later volumes later in the century so it's certainly unfair to dismiss future parts on the basis of the first. However I can understand people who didn't like The Black Dossier (I do, a lot), not liking this as it's more in keeping with TBD's tone than with the first two books.
I particularly liked the Prisoner of London, trapped in space but not in time.
There seems to be some confusion over the identity of Quartermain Jnr. As far as I am aware he is Allan Quatermain made immortal by going, with Mina Murray, through Ayesha's fire. Oliver Haddo is the equivalent of Aleister Crowley in a W. Somerset Maugham story.