As with many other typefaces, there are different cuts for different sizes.

Storm Type for example offers Baskerville 10 Pro for text
http://www.stormtype.com/typefaces-fonts-shop/families-77-baskerville-10...

I think what I'm really asking is about the intention of the original Baskerville design — was it for books?

Does that unique Baskerville 10 for text sizes only exist because John Baskerville's design wasn't suited for text?

Yes, Baskerville's design was for books.

In Baskerville's day, punches for metal type were cut at different sizes, and the designs of the letterforms were altered to make them suitable for those different sizes (lower contrast for smaller point-sizes, for example).

Baskerville 10 as a digital font, thus, is not a correction to Baskerville's design, but rather somewhat of a restoration of the size-specific sensitivity that was standard in metal type and jettisoned in most digital type.

Related threads of potential interest:

http://typophile.com/node/76260
http://typophile.com/node/68011
http://typophile.com/node/70149

Plenty about all manner of Baskervilles here at Typophile:

http://www.google.com/search?q=site:typophile.com%20Baskerville

Great, thanks, all!

Something else to worry about:
There are two strains of Baskerville: the original and what's termed the "Fry's" style, which was a competitor's interpretation of the original. The Fry's tends to lean more heavily towards display usage, although some (like ATF) have made it in proper text sizes/cuts.

And, FWIW my favorite is Fountain's:
http://www.fountaintype.com/typefaces/baskerville-1757

hhp

My favorite is the plain old original, or Monotype's revival of it. My first-year Physics textbook (Halliday and Resnick) was set in Baskerville, and so I think it is a good text typeface.

It is a bit wide, just as Century Expanded is a bit condensed. But that just affects how one uses it - which size, what leading.