Use of Weapons by Iain M Banks

The third book in Banks’s Culture Series concerns Cheradenine Zakalwe, an agent for the Culture’s Special Circumstances unit, employed to change the destiny of other civilisations and planets by intrigue, dirty tricks or even military action.

Zakalwe is humanoid, but not of the Culture, and finds his first time on one of the General System’s Vehicles, the Culture’s immense craft carrying millions of people through interstellar space, quite bewildering. A fighting man, he is unused to a life of leisure and limitless recreation. However, he does find time to indulge in one of his favourite hobbies: drinking.

A GSV contains an interesting diversity of drinking companions and some of the people he meets are clearly alien, even more so than Zakalwe:

It had eight limbs, a fairly distinct head with two quite small eyes, curiously flower-like mouth parts, and a large, almost spherical, lightly haired body, coloured red and purple. Its own voice was composed of clicks from its mouth and almost subsonic vibrations from its body; a small amulet did the translating.

This particular alien is also an agent of Special Circumstances, and is quite happy to spend its downtime with other spies:

It banged its drink-bowl on the table to attract a passing tray. “Let’s have another drink; see who gets drunk first.” “You have more legs.” He grinned. “I think I might fall over more easily.” “Ah, but the more legs, the bigger the tangle.” “Fair enough.” He waited for a fresh glass. To one side of them was a small terrace and the bar, to the other a gulf of airy space. The ship, the GSV, went on beyond its apparent boundaries. Its hull was pierced multitudinously by terraces, balconies, walk-ways, open windows, and open bay doors. Surrounding the vessel proper was an immense ellipsoid bubble of air, held in side dozens of different fields, which together made up the Vehicle’s real – though insubstantial – hull. He took up the recharged glass when it arrived, and watched a puttering, piston-engined, paper-winged hang glider zip past the terrace; he waved at the pilot, then shook his head. “To the Culture,” he said, raising his glass to the alien. It matched his gesture. “To its total lack of respect for all things majestic.” “Agreed,” the alien said, and together they drank... The alien was called Chori, he found out later. It was only due to a chance remark that he discovered Chori was a female, which at the time seemed hilariously funny. He woke up the next morning lying soaked as well as soused half underneath a small waterfall in one of the acc section valleys; Chori was suspended from a nearby railing by all eight leg-hooks, making a sporadic clattering noise that he decided was snoring.

Sadly Banks does not tell us which of them ran out of legs first...