I'm going to be homeschooling my 9 yr dd old next year (for 5th grade). The SOTW books look really interesting, but I understand they are Christian based. Is this true? And if so, how strong is the religious tone? I'm not adverse to an underlying current of religion, but since we are not religious ourselves, I don't want something that is strongly biased in it's overview of the time period. Also, which SOTW would you recommend I use for my dd. Is it best to use the books in order, from 1-4?
It is written from a Christo-centric bias. But nothing that's difficult to work with. For instance, they cover ancient Egypt, and Mesopotamia, but make sure you realize that the included stories are myths these people believed. When they present Moses, an informed reader might mistake the story for verified history. But a little bit of clarification fixes the problem. I would recommend starting at the beginning. The first Chap. is a nice intro to the concepts of "History" and "Archeology".
Definitely Christian, but relatively easy to work around. When it says "There was a man named Moses whom God spoke to" you just insert a sentence previous to that: "This is a story from the Christian bible about some people living in Egypt at around this time." Other stories from other cultures and religions are presented as cultural glimpses, not as fact. Beowulf is in there, for instance. You just need to present the bible stories similarly.
We're secular, and happily use them.
There's the bits that others have mentioned that imply that Christian stories are true while stories from other cultures/religions are myths. The second volume has a lot of Christianity in it, but that's what was going on in Europe during that time period, and it's not saying "These beliefs are true" but "This is what was happening" - it's more of a problem of emphasis on Western culture than specifically Christian bias.
Treating Bible stories as historical fact (notably ones for which there is no historical backing--such as Moses--to me is a very big Christian bias. That and the way hunter-gatherers and nomads were equated as the same thing in the first chapter (with the implication that they didn't bathe regularly whereas farmers with a city would) pretty much turned me off to the series.
There are definite biases, but, as others said, it isn't difficult to deal with them. I reword some sentences, and add others. I also use the biases as an opportunity to teach my son about different viewpoints, and about using critical thinking skills. It doesn't take much extra time. It may be more challenging to address the biases if your child is reading the books herself rather than you reading them to her.
Our local Barnes and Noble carries them... maybe you could see if one of the book stores near you does too so you could flip through the actual book and get a feel for them?
Personally they were "too Christian" for our family... we're not Christian but we're also not secular (we're Heathen, a Norse religion) and there was just too much I'd have to change. Not necessarily specific sentences, but the entire tone of some sections was just "off" for us. Some of the illustrations were a problem for our family too (bright shiny cross, horned helmet wearing "viking", etc). I was glad I'd had a chance to browse them (and I borrowed a copy from a friend for a few days to give certain sections a deeper read) because they do get such great reviews, even on secular homeschooling boards, and I know I've been tempted a few times to pick them up!
(for general world/narrative history we've been using A Little History of the World by Gombrich... it has it's own problems, but they're easier for me personally to deal with since they're mostly stuff I need to fill in rather than things I need to weed out and the storytelling tone works great with my younger kiddos)