The photo of the pattern book was picked somewhere online, but it’s the same 50-pattern book as mine.

This pattern drove me crazy for almost four decades! The first problem was that the yarn manufacturers used one term - worsted weight - to refer to a thinner thickness of yarn sometime pre-1960 and the same bleeping term to a thicker yarn - what we now call worsted weight. The earlier edition of this book called for US size 4 needles, and for smaller squares to boot!
Inexperienced as I was in 1966, I just figured it was something I was doing wrong that was preventing me from ‘getting gauge’. I put the original aside and worked on other projects, trying to acquire knitting experience and expertise.

Decades later - after my mother’s death in March 1997 - her more recent edition of this pattern book (with a full hundred stitch patterns in it and with the sampler afghan made up of fewer and larger squares) turned up when I was emptying long-forgotten boxes in her attic. http://www.ravelry.com/patterns/sources/fleisher-bear-bra...
I compared it to mine. With the later edition’s needle sizes and the same worsted weight yarn I’d begun with, I had no problem making the squares to its gauge.

So, I experimented. I tried working the original pattern book’s directions with baby and sport weight yarns. Eureka! With no other adjustments, I was turning out squares exactly the size the book called for! I was so happy about the breakthrough, that I kept right on making the squares with half of the squares in off-white and the other half in whatever sport/baby weight I had on hand. Yippee! I won!!

Practical notes:
I loathe sewing bits together. This is crocheted together using Priscilla Hewitt’s Flat Braid Joining Method. http://www.ravelry.com/patterns/library/flat-braid-joinin...
http://priscillascrochet.net/free%20patterns/Afghan%20Edg...
Yes, it increases the overall size, but it will never fall apart in use or the wash.

Despite the visible differences, my non-geometrically-correct ‘squares’ each have a round of single crochet - odd number, 29 I think - so as to make the joining work without fudging.

No, I didn’t block my ‘squares’. It’s all synthetic yarns anyway. Despite its thinness, it’s surprisingly warm. Can’t see the irregularities of the non-square ‘squares’ in the dark, so that’s all good.

No, I didn’t place the squares as the pattern book suggested. In an effort to balance things, I placed the ‘fatter’ ones next to the ‘skinnier’ ones.

Half of the squares are cream coloured sport weight yarn from a single (HUGE) ball - probably Red Heart.
The rest are a hodgepodge of similar-thickness yarns. Heck, a few of the squares are two-toned, because I ran out of yarn and didn’t want to rip!
The joining yarn is all one batch of baby-pink.
The border a batch of baby-hued variegated, but it only shows at the edge of one photo.

I learned that it’s lots easier to work the two same-stitch-pattern squares at the same time on the same needles; it saves having to read each line of each pattern twice.