From The FreeOnLineDictionaryOfComputing:
A dialect of the LispLanguage developed in 1967 by Bolt, Beranek and Newman (Cambridge, MA) as a descendant of {BBN-Lisp},. It emphasises user interfaces. It is currently supported by {Xerox PARC}, [XeroxParc].
Interlisp was once one of two main branches of LISP (the other being {MacLisp},). In 1981 {CommonLisp}, was begun in an effort to combine the best features of both. Interlisp includes a Lisp programming environment. It is {DynamicallyScoped}, [uses DynamicScoping]. NLAMBDA functions do not evaluate their arguments. Any function could be called with optional arguments.
["Interlisp Programming Manual", W. Teitelman, TR, Xerox Rec Ctr 1975].
I recommend ["INTERLISP : the language and its usage", S.H. Kaisler, John Wiley & Sons, 1986], sometimes titled just "INTERLISP".
Also see TheEvolutionOfLisp.