I suspect based on the Wikipedia article for Quastler that this may also be the same book as the slightly differently titled Essays on the Use of Information Theory in Biology. (Urbana: University of Illinois Press, 1953). There’s also a 1955 review of the text with this name available as well.
Google uses the first title with 273 pages and the Symposium text specifically cites Information Theory in Biology as the correct title several times.
The tough part seems to be that there are very few copies available online and the ones that are are certainly used, in poor condition, and priced at $100+. Ugh…