“Slow” in this case is a relative term. She’s number five on the New York Times bestseller list this week and was as high as second last week, missing the top spot only because she had to compete with Bush’s presidential memoir. Is the bar for Palin Inc. so high at this point that anything less than number one is failure?

After “Going Rogue” sold a jillion copies — maybe.

“America by Heart,” Palin’s new memoir, has logged disappointing receipts since it officially went on sale late last month, publishing sources say. Although the book is second on the New York Times bestseller list this week (behind former president George W. Bush’s memoir, “Decision Points”), its publisher, HarperCollins, hasn’t ordered a second printing – a sign that sales haven’t been overly brisk…

“America by Heart” (subtitle: “Reflections on Family, Faith and Flag”) got a more modest launch [than her first book]. HarperCollins’s initial press run was 1 million copies, suggesting that the publisher recognized that “Heart” was not likely to repeat the success of “Rogue.”…

One theory within the publishing industry is that Palin is overexposed, at least in terms of drawing readers.

Palin’s first book, published only a year ago, sold well enough to sate Palin’s supporters, her enemies and the merely curious. It was such a strong seller in hardcover that it crowded out demand for the book in paperback and for the sequel of sorts, some in the industry say. The paperback version of “Going Rogue” has not made the bestseller lists or gone into reprint since it was issued with a new afterword by Palin in August.

Don’t forget, though, that “Going Rogue” had plenty of campaign dirt in it too, which opened it up to a much broader demographic than just Palin fans. The fact that it was a biography also surely lured people who are intrigued by Palin the person even if they’re less enthused by Palin the politician. The new book isn’t going to retain those audiences so there’s no reason to expect it to do as well. It’ll still sell big — there are a lot of Palinistas out there — but it’s probably aiming for the same level of success as her TV show: Not epochal ratings, but still impressive (and steadily so). In fact, I’m tempted to say that as a general rule politicians’ second books always do worse than their first just because there’s less new material available for the second book. They’re necessarily forced to write more about politics and ideology than they are about biography, which makes for a drier read. The one exception to that rule, of course, is Obama; I can’t find hard numbers but I’m reasonably sure that “The Audacity of Hope” outsold “Dreams from My Father.” But then, “Audacity” had the stellar advantage of being released right around the time The One was gearing up to run for president. There was a lot of buzz around him at the time but he was still an unknown quantity, so naturally the public craved insight into his worldview. It was superb timing. Even if Palin ends up running and releases a new book to coincide with the announcement, her sales won’t be as high because her views are much better known already than his were at the time.

Speaking of Obama and authorship, his new children’s book is number 20 on USA Today’s bestseller list (Palin is ninth) and number 37 on Amazon (Palin is 30th).