That's code for 101.

No. It's code for the thickest, densest book on the subject that you're ever gonna not read, as it actually assumes you're experienced in the subject and goes into everything except intro level topics.

See e.g. Petzold, et al.

I'm getting flashbacks to Spivak, who wrote a 2000 page "introduction" to differential geometry.

To be fair to Spivak, he did say it was comprehensive introduction. :)