Wow! I’ve heard such positive reviews on the book Socks Soar on Two Circular Needles and I’m excited to try it out. But, I need to know one thing before adding it to my Christmas list: What size needles do you need? This info would be much appreciated, thanks! 
Needle size always depends on the type of yarn you use. The book teaches a technique so you can really use any yarn you want although it may suggest a yarn size for the tutorial. For your average fingering weight sock yarn you’d use a US 1 or 2 usually. Heavier yarns require larger needles.
and i prefer us0 for my socks with fingering weight yarn. i just love the look of such a tiny stitch. <3
I just flipped through my copy and the majority of the patterns call for sizes 1, 2 or 3 depending on gauge.
There is one pattern for felted booties that calls for 10.5 or 11s and one pattern that calls for sizes 3 or 4.
Jan is right – the book teaches how to adjust any sock pattern to be knit on 2 circulars. I’m not really that excited about the patterns included in the book so I just used the part on how to adapt a pattern and am making the Embossed Leaves socks from another book using the 2 circs method outlined in the Socks Soar book.
To me that made the book worth having.
Best,
Susan