I don't know if it's really fair to talk about a book before you finish it, but in this case I don't think my first impression is going to be too far off the mark. Lies My Teacher Told Me
made quite a splash a few years ago, and gets pointed to quite a bit by people who think the public schools ought to be used for social change and not education (see SCSU Scholar's take on that whole controversy here: http://scsu-scholars.blogspot.com/2004_04_01_scsu-scholars_archive.html#108135481856317282
) the way they theoretically are now.
Since this book hits close to home - I'm working towards certification as a Social Studies/Spanish teacher - I picked it up out of the library at St. Mary's and thought I'd give it a look. I can't say I'm overly impressed. James Loewen (a sociology prof at U. Vermont) isn't a historian, but he knows the field well enough to slag the current crop of U.S. History texts for being the boring, homogenized piles of putrescent oatmeal that they are. Unfortunately, he seems to think that the cure for this is by taking the diametrically opposed tack of throwing in all the negative stuff that gets left out of the standard texts - like, for example, George Washington owning slaves, Columbus kicking off the slave trade in the Caribbean, and so on. This would certainly be more exciting for the teachers and the kids, right up to the point where outraged parents got the teachers fired and the new texts thrown in the recycling bin.
Loewen seems to understand that most parents want their kids to feel good about America and its institutions, but he doesn't seem to agree that this is a good thing. He also doesn't seem to grasp that we're trying to teach kids the basic facts on which they can build their knowledge & understanding of American history, and we only have so many hours in a school year to do this. If you take an honest look at American history, what is more important about G. Washington? Is it the fact that he was a highly-regarded political and military figure of the 18th century in America, or that he was a childless slaveholder? Likewise, in the context of American history, is Columbus more important for his establishment of Spanish colonies in the Americas or for his introduction of massacres and slavery? You have to hit the high points, and you have to decide what kind of history you're going to teach. People will go back and find out the whole story on their own if they want to - you're just trying to give them a precis of 200+ years of European exploration and exploitation. In that context, the Norse exploration of Greenland and Newfoundland just isn't that important, still less the hypothetical African voyages to South & Central America.