All 12 Uses of

however
in
Oryx and Crake

No hope of whittling that kind of game, however.†
p. 40.8

however = a word used to connect contrasting ideas as when using "though", "in spite of that", "in contrast", "nevertheless", etc.

In the long run, however, the benefits for the future human race of the two in combination would be stupendous.†
p. 304.8 *

however = a word used to connect contrasting ideas as when using though, in spite of that, in contrast, nevertheless, etc.

Crake, King of the Crakery, because Crake is still there, still in possession, still the ruler of his own domain, however dark that bubble of light has now become.
p. 333.9 *

however = regardless of how

He was admired for this, however: it showed he was good at his trade, and the children would be in competent hands.†
p. 118.5 *

Uncle En had experience, however: he treated the new children as if they were cats, he gave them time to get used to things.†
p. 127.2

However you look at it, he'd said, what it boiled down to was eating your own shit.†
p. 159.3

He had no further wish to try it out himself, however: he had enough problems without his penis bursting.†
p. 296.5

Definitions:

(1) (however as in: However, complications may...)
though (or another expression that connects contrasting ideas)

(Based on idea 1 we might not expect idea 2, but this is a way of saying that even though idea 1 exists, we still have idea 2. Synonyms include in spite of that, despite that, nevertheless, nonetheless, on the other hand, in contrastand but.)
(2) (however as in: However much she tried...)
to whatever degree (regardless of how much; or whatever unspecified amount)
(3) (however as in: However you do it, get it done!)
in whatever way
(4) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much more rarely (and arguably incorrectly), however can be used to intensify the word how, as when one says "However did you find her?" Grammarians would suggest using two words for that usage: "How ever did you find her?"