NEW YORK (AP) _ First of all, dear viewer, you must be clear on the distinction between ``bad'' and ``BAD.''

According to Craig Nelson, ``bad,'' at least when applied to TV shows, is that which is boring and stupid and crying for clicker-oblivion.

On the other hand, BAD television (that's all caps, gentle viewer!) is a joy forever.

At least it is for Nelson, who cared enough to watch the very worst compiling ``The Very Best of the Very Worst BAD TV'' ($9.95; Delta Trade Paperbacks).

What he ended up with is a funny read, a rigorously researched reference, and a shrewd celebration of human folly by people who brought you BAD TV like ``Where's Everett?'' (1966; Alan Alda and Patricia Smith adopt a baby who's not only from another planet but invisible).

The book's first section is ``BAD Classics Hall of Fame,'' whose dozens of entries include ``The Brady Bunch,'' ``Mod Squad'' and ``Lost in Space.''

Then Nelson moves on to his self-styled ``Tammi Awards,'' named in honor of that great symbol of waste, Three Mile Island. For each television genre (sitcoms, variety shows, even kid shows, infomercials and made-for-TV movies), Nelson confers from one to six Tammies on such deserving BAD TV as ``She's the Sheriff,'' ``Lancelot Link, Secret Chimp,'' ``It Pays to be Stupid,'' ``The Brady Bunch Variety Hour,'' the long-ago ``Studs' Place'' (1949), and then his most recent inclusion, ``Late Night with Conan O'Brien.''

Along the way, Nelson devotes a chapter to BAD things that happen to good (TV) people. ``Life with Lucy'' (1986's painfully short-lived return to sitcoms by a septuagenarian Lucille Ball) and ``David Cassidy _ Man Undercover'' pratfall into this category.

Another chapter, ``Curses!,'' plumbs certain mysteries of the BAD-TV universe, pondering, for instance, why Tim Conway could never make it as a series star (and darnit, did he ever try, try, try!).

Meanwhile, this book is a virtual ``Poor Richard's Almanac'' of BAD-TV maxims. Check out these words to live by:

_ If you're a cop, it may be more trouble than it's worth to have a partner who's from another planet.

_ If you're married to, best friends with, or next-door neighbors of your polar opposite, it'll be a living hell for you, but a laugh-riot for your friends.

And, of course:

_ If your life is dull, buy a chimpanzee.

The idea for ``BAD TV'' came to Nelson in, aptly enough, a vision.

``With the coming 500-channel world of television, there will be more and more room for horrible shows,'' Nelson reasons. ``I saw the need for a guide to all of them.''

Thus did he set forth on his vision quest.

By day a just-turned-40 editor who specializes in pop-culture books, this unabashed fan of television devoted his after-hours to compiling lists, tracking down shows and screening his BAD contenders.

Don't think it was easy.

First of all, many of the most deserving series were _ not surprisingly _ lasted for just the blink of an eye. So where to search for this twilight cache of BAD video?

``Places like the Museum of Television and Radio collect only the BEST of television,'' notes Nelson with a trace of disapproval. ``I think they ought to reconsider their mission.''

Fortunately, perseverence _ and assistance from several private collectors Nelson admiringly terms ``hard core'' _ unearthed much of what he was seeking, enabling him to screen for himself fully half the programming that earned its way into his book.

And plenty that didn't: ``The most hideous part of the research was, I had to spend hundreds of hours watching things that were bad BUT WEREN'T BAD ENOUGH!

``Of course, with a lot of shows, you don't have to see it to know it qualifies,'' Nelson adds. ``My all-time favorite _ I could never get my hands on it, but I'm still dying to see it _ is `Poochinski.' It's about a cop killed in the line of duty who is reincarnated as a crime-fighting bulldog with gas.''

'Nuff said: This NBC sitcom (with one fateful airing in July 1990) scored 5 Tammies, sight unseen.

So hail ``Poochinski'' and history's other BAD TV! Thanks to Nelson's book, these classics will never die.

___

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