Paul Campos, the University of Colorado Law School professor who writes the incendiary Inside the Law School Scam blog, is back at it, with a new book of advice for would-be law students.

Campos said he was inspired to write Don’t Go To Law School (Unless) — an electronic book slated to go on sale on Amazon.com this week — in part because so many prospective law students have asked him for counsel about whether they should enroll.

“I’m trying to make it clear to anybody who is considering going to law school right now that they ought to consider that to be a fairly risky endeavor, and should do that in only a fairly narrow set of circumstances,” he said.

For example, under no circumstances should you go to law school without a firm desire to become a lawyer; without exploring what working as a lawyer really is like (watching Law & Order doesn’t count); and without investigating whether your career goals are realistic (you can probably forget about practicing international sports law), the book argues.

Going to law school because you don’t know what else to do with a liberal arts undergraduate degree was never a good idea, Campos writes, but it’s a particularly poor choice when the average law student graduates with $150,000 in loan debt and a well-paying job is hardly guaranteed.

The book’s critique of law school will sound familiar to regular readers of Inside the Law School Scam, although the tone is somewhat softer. “With the book, I tried not to be polemical,” said Campos, whose sharp-elbowed blogging has turned off more than a few of his colleagues in legal academia. “My goal was to analyze the information in the most disinterested way I could, so people could make up their own minds.”

Still, as the title suggests, the book offers potential law students more discouragement than enthusiasm. Campos cites the latest statistics about the declining legal job market for new law graduates and growing debt loads, plus deep skepticism about the value of law school curricula and the versatility of a J.D.

For would-be students who clear Campos’ initial hurdle, in that they have a real interest in practicing law, the book suggests an extensive examination of whether a law degree makes economic sense. Prospective students should take into account the debt they will assume, their odds of landing the job they want and the salary they will likely earn. All while avoiding what Campos calls the “Special Snowflake Syndrome” — the tendency to be overly optimistic about one’s prospects.

“Almost everyone who goes to law school plans to work exceptionally hard and finish in the top 10 percent of the class,” the book says. “Ninety percent of these people are going to see their plan fail.”

Campos suggests ways to read the jobs data provided by individual law schools and the American Bar Association — focus on the percentage of graduates in full-time, long-term jobs that require a J.D.; look at three categories of “real legal jobs” open to new graduates — working at a private law firm, being a state or local prosecutor, or being a public defender. Campos counsels that new graduates do get hired by public-interest law organizations, but in such small numbers that the career path shouldn’t play into a prospective law student’s decision.

In addition to would-be law students, Campos said, he also wrote the book to help bring baby-boomer lawyers and pushy parents up to speed about how law school and the legal market have changed, in hopes they won’t advise their children that law school is always a solid decision.

“The cost of law school and the likely future return on a law degree have both changed so radically over the past 20 years, and especially over the past decade, that many older people, and even many older lawyers, have no idea how risky a proposition law school has become,” the book reads. “Rather than relying on the conventional wisdom, do your own research about costs and likely outcomes.”

Ultimately, Campos suggests, paying full tuition makes sense at only a handful of elite schools, and paying a significantly reduced tuition only makes sense at between seven and 10 “truly national law schools.” Even accepting a free ride makes sense at only about three dozen “good regional schools,” by Campos’ estimate.

“The most important thing for any prospective law student to keep in mind is that, at present, the large majority of law graduates — perhaps 80 percent — end up worse off after going to law school that they were before they enrolled,” the book reads.

Contact Karen Sloan at ksloan@alm.com.