Omnibus of: FAR OUT (1961) + IN DEEP (1966) + OFF CENTRE (1969) + TURNING ON (1967.) What a colossal bargain! Damon Knight is at his best at shorter lengths; 20 of these stories make up the bulk of The Best of Damon Knight. Very strongly recommended!
Note that British versions of In Deep and Turning On are used - the first omitted "The Handler" / the other added it - so you don't miss anything. Off Centre is the 1969 British expansion which adds 3 stories to the 1965 American collection Off Center.

Far Out (1961) - the first collection of stories by Damon Knight. 11 out of 13 of these can be found in the 1976 restrospective The Best of Damon Knight - just to give you an idea of the quality of these stories. Knight is a master of the short SF story - don't form your opinion of him based only on his novels. I recommend this (or any other collection of his stories/novelets.)

(Introduction by Anthony Boucher)
To Serve Man
Idiot Stick
Thing of Beauty
The Enemy
Not with a Bang
Babel II
Anachron
Special Delivery
You're Another
Time Enough - (original title= "Enough Time")
Extempore
Cabin Boy
The Last Word

Original appearances from 1950 to 1960 - in Galaxy (4), Star SF #4, Venture, Magazine of F&SF (2), Beyond, IF, Amazing, Infinity, Satellite.

In Deep - a collection of stories by Damon Knight. This is the contents of the revised 1964 British edition (and later reprints), which omitted one story ("The Handler") from the 1963 American version. That story was added to the 1967 British edition of Turning On - so that buyers of the British versions wouldn't miss any stories.

Four in One
An Eye for a What?
Stranger Station
Ask Me Anything
The Country of the Kind
Ticket to Anywhere
Beachcomber

Original appearances from 1951 to 1957: (4) in Galaxy, (2) in Magazine of F&SF, plus Imagination.

Off Centre - a collection of stories by Damon Knight. This is the expanded 1969 British version which adds 3 stories to the 1965 American Off Center.

What Rough Beast
The Second-Class Citizen
Be My Guest
God's Nose
Catch That Martian
Dulcie and Decorum
Masks
To Be Continued

Original appearances from 1952 to 1968: (2) in F&SF, (2) in Galaxy, plus IF, Fantastic Universe, Rogue, and Playboy.

Turning On - a collection of stories by Damon Knight. This is the contents of the 1967 British edition, which added one story to the 1966 American version. "The Handler" had been omitted from the British edition of In Deep - so the inclusion here makes sure that buyers of the British versions don't miss any stories.

Semper Fi - (original title= "Satisfaction")
The Big Pat Boom
Man in the Jar
The Handler
Mary - (original title= "(An Ancient Madness")
Auto-Da-Fe
To the Pure
Eripmav
Backward, O Time - (original title= "This Way to the Regress")
The Night of Lies
Maid to Measure
Collector's Item - (original title= "End of the Search")
A Likely Story
Don't Live in the Past

Original appearances from 1951 to 1966: (6) in Galaxy, (3) in Magazine of F&SF, plus Analog, Rogue, New Worlds, Worlds of Tomorrow, and Infinity.