TOWARD the middle of ''Valediction'' we come upon Spenser, Robert B. Parker's private-eye hero, studying computer printouts that relate to his current case. As he sits on a bench in downtown Boston, Spenser tells us: ''I put my sunglasses into my breast pocket and looked around. No one was watching. I put my hand unobtrusively into my inside jacket pocket and came out with a pair of half glasses and put them on. I looked around again. No one seemed to have noticed. I looked down at the printout. Ah-ha. There it is. I wear these only to see.''
In ''Valediction,'' Spenser's 12th case, Parker clearly wants to portray him as more mortal. Spenser complains: ''Time was when I could remember everything. Now I had half glasses and a notebook. Next thing I'd have a midlife crisis.''
Actually, Spenser is having a crisis. Susan Silverman, his longtime companion , has left him for a job in San Francisco. ''I have to be alone,'' she says.
Susan's departure creates a vacuum in Spenser's life. Some of this empty space is filled by Paul Giacomin (the teen-ager Spenser more or less adopted in ''Early Autumn''), some by a more sympathetic and visible Hawk (Spenser's sidekick who, says Spenser, is so tough ''he could guard Yugoslavia alone''), and some by various minor characters Spenser meets in the course of detecting and in developing a new social life.
For all that, this is a depressed Spenser. When, at one point, Hawk asks, ''You care if somebody blow you away?'' Spenser simply says ''No.''
Despite his emotional flatness, Spenser is still his witty and physically formidable self, still capable of vintage remarks. Replying to a comment from someone checking his detective's ID - ''Not a flattering likeness'' - Spenser responds, ''It didn't have much of a start.''
Parker's writing in ''Valediction'' is the best he's done since ''Looking for Rachel Wallace.'' It's taut but humorous - and cleverly plotted.
Yet the focus of Parker's series is always Spenser. Spenser is growing as a character, expanding in ways that suggest Parker plans to keep him around and to find many more interesting things for him to do.
This brings us to another capable private-eye novel - this one written by a woman. The detective genre is male-dominated, and it has always been so. Writers like Parker, Stephen Greenleaf, Arthur Lyons, Jonathan Valin, and Loren D. Estleman have been carrying on the tradition established by Hammett and Chandler.
But now there are women writing private-eye novels of quality. The best of the group is Sara Paretsky, and her detective is Chicago-based V. I. Warshawski.
''Deadlock'' is Warshawski's second outing - ''Indemnity Only,'' the first, appeared in 1982. She is convinced that the supposedly accidental death of her favorite cousin, former hockey star Boom-Boom Warshawski, was no accident.
She's right, of course (detectives always are, aren't they?), and she sets to work on figuring out why Boom-Boom fell off a dock while working for the Eudora Grain Company. By the novel's end we've learned an awful lot about shipping on the Great Lakes on our way to discovering what happened to Boom-Boom.
Author Paretsky is an insurance executive, so, not surprisingly, Warshawski specializes in corporate crime. This does not mean, however, that there is no violence. Warshawski suffers her share of beatings, yet is hardly deterred by them. She also has her men friends, but none of her relationships with them could be called casual.
Warshawski is an appealing and believable character, and she has developed perceptibly in ''Deadlock.'' Given Paretsky's ability to handle plot and prose, Warshawski should be even better when we see her again.