Is there a single, non-technical book on the basic technologies of the
internet age ... i.e. whatcan I read to be conversant with my tech
sector clients?

I highly recommend a book called "The Cuckoo's Egg" by Clifford Stoll.
Its actually a very intriguing true story about a Berkely Professor
who knew very little about the Internet. One day he noticed a $0.03
accounting error between two programs, and began digging at it to
discover international cold-war computer espionage. Along the way he
not only learns about the fundamentals of the Internet, he does the
job best I have seen of translating this for the non-technical reader.
And it is a very well-written and intriguing story. Although dated
(the graphical world wide web didn't exist back then) it will give you
a great foundation/history on the actual Internet while gripping your
attention with a fascinating story.

You can find it at Amazon. Brand new its less than $12 and there are
used copies for less than $4.

Wasn't Stoll an astronomy student and the accounting error 75c ?
The book does manage to remain non-technical.

Picking just some parts out of "TCP/IP Illustrated, Volume 1" by W.
Richard Stevens might also help you.  The whole thing might be too
much.

I recommend this book
How Computers Work, 8th Edition (Paperback)
ISBN: 0789730332 

I actually gave it to my non-techie girlfriend so she could understand
me a little more. It's an easy read with a lot of good illustrations
to explain the terminology.

What exaclty you want to learn about?
Is it about internet and its working?
or 
Technical details like protocols too?
or
What actually, if I understood qestion wrong?
Your elaborated answer will help to suggest you a better option.

Regards,