The summer's -- and possibly the year's -- best series ends its first season tonight with the same sentiments it has evoked throughout its run: wistfulness, isolation and melancholy.

AMC's "Mad Men" (10 p.m.) may not be the most joyfully entertaining show, but it is completely engrossing, with an understanding of its characters and their psychology that's unsurpassed in prime-time television.

If you're a fan of smart, sophisticated TV dramas (e.g. "The Sopranos," "The Wire," "The Tudors") and you didn't get on the "Mad Men" bandwagon, at this point you're better off waiting until the show is out on DVD. It will be an almost perfect TV-on-DVD experience, because more than most series "Mad Men" truly creates a world and sucks viewers into its layered, complex experience.

When "Mad Men" began in July, it was easy to embrace its authentic period look: the sets, the costumes, the colloquialisms of the era. But after the first couple of episodes, I began to worry that might be all there was to the show. The emphasis on style and predictable differences in the workplace from 1960 to 2007 seemed to supersede the substance of all-important character development.

No sooner did I begin to worry about the show's future than creator Matthew Weiner and his writers began to mine their characters for the rich details they already had extracted from the show's setting.

Viewers learned suave ad exec Don Draper (Jon Hamm, a master of subtlety) had a secret past, one that was finally exhumed in last week's episode after underling Pete Campbell (Vincent Kartheiser, excellent at showing both his character's unctuousness and loneliness) threatened to reveal his secret to boss Bertram Cooper (Robert Morse). Any other show would have dragged out this blackmail plot for a half-dozen episodes; "Mad Men" disposed of it in one mercifully efficient hour.

Every character at the Sterling Cooper ad agency has shown growth over the course of the show's 13-episode first season, from assistant Peggy (Elisabeth Moss), who gets two surprises in tonight's season finale, to ad men Kenny Cosgrove (Carnegie Mellon University grad Aaron Staton) and Roger Sterling (John Slattery), who has been sidelined in his horn dog pursuits by a heart condition.

Other matters of the heart take a prominent role in tonight's commercial-free season-ender as all the pieces regarding Don Draper and his attitude toward his birth family and the family he shares with his wife, Betty (January Jones), come together in a presentation to Kodak executives. His colleagues think Don's pitch is masterful, but viewers will know it's a view into his conflicted soul.

Betty, too, has had a difficult time. Emotionally fragile and physically isolated, she feels loss from the death of her mother and a disconnectedness from her often-absent husband. In tonight's finale she makes a discovery, though not necessarily the one she expects, and she begins to use her newfound knowledge to her advantage.

"Mad Men," already renewed for a second season to air next year, is not a series you can talk to your spouse through or read a magazine while watching. To fully appreciate the nuances of character and story, viewers must give it their full attention. Perhaps in today's world of multitasking TV viewers -- watching TV, IMing friends online, balancing the checkbook -- "Mad Men" asks too much. But for anyone who yearns for more depth and complexity from their prime-time entertainment, few, if any, programs are as satisfying.