Disclaimer: although I have had nothing to do with this book and I have never met the author (we live at the antipodes of each other), I was the technical reviewer for her previous book - and I am the author of two SQL books, none of them for beginners.
Knowing Clare's style, I have been extremely surprised by some of the reviews of this book, which are rather harsh. I got a copy of "Beginning SQL Queries", and read it to have an opinion of my own.
Several reviewers complain about the references to algebra and calculus; I think they have missed Clare's point, which was to show that there are two writing styles with SQL. She could have called them style A and style B, but unfortunately she is rather precise in what she writes and chose to call them by their received names of algebra and calculus, which I agree are dirty names. Which one is algebra and which one is calculus is usually something I forget very fast, and I've practiced SQL for a quarter of a century; believe me, you can use both styles without knowing their names.
I also take objection to one reviewer's comment that "it is clear the author doesn't actually understand SQL. A table alias is not a 'row variable'". Perhaps Clare didn't make her point clear enough; but when you write a correlated subquery, as in
from ta outer
from tb inner
where inner.id = outer.id)
"outer" (the table alias) in the subquery actually refers to the current row from the outer query. Perhaps an unusual way to introduce the topic; but I have always believed that the goal of a book should be to intellectually challenge the reader and bring him or her to see the topic in a different light.
All this being said, I'm not convinced by some aspects of the book. For one thing, if the author actually starts from the "novice" stage, she doesn't really bring the reader to the "professional" stage in my humble opinion; the coverage of topics like indexing is light, and none of the examples is even remotely as complex as what I routinely encounter. This makes the introduction (fortunately discrete) of formal notations look like an overkill with no real added value. Better to concentrate on the figures, which are extremely clear.
If you just wish to make some quick and dirty SQL job, "Beginning SQL Queries" is probably not a book for you - I guess that any tutorial on the web and a bit of trial and error will get you started. You won't go very far, but sometimes you don't want to.
I rather see this book as a good bridge between college and the professional world - it combines the rigor of text books (although it doesn't theorize, all the key points from the theory are here) with the conversational tone of books that are aimed at the professional world; strictly correct without being dry. It will not turn you into a full-blown database professional, but if what you have seen - or not seen - at school is hazy and if you are serious about ensuring that you have sound foundations, reading "Beginning SQL Queries" is a good way to start.