That’s what video says.
It was released approximately at same moment than 2.82.
So, content is probably based on 2.81 or on master between 2.81 and 2.82 or on d.b.o tasks at that moment.
2.82 did not change basics a lot compared to 2.81.
Most of 2.82 features were about advanced stuff. (Mantaflow, UDIM, USD, Custom AOVs, Denoiser…)
Most of Interface refactoring after 2.80 happened in 2.81 (new File Browser, new Outliner, New Sculpt mode, library overrides, EEVEE light shadows, Grease Pencil brush presets and guides…)
2.83 features are also mostly about advanced stuff and new additions that have no impact on basics.
(Volume Object, Mantaflow bugfixes, VR…)
It will be a pity to miss EEVEE passes, Cycles Adaptive Sampling and Sculpt Face Sets & auto-masking when learning 2.83 with this book.
But that does not make a lot of things to discover by yourself.
The only thing that would be a bad idea is : to try to learn Grease Pencil in 2.83 with docs anterior to 2.83.
UI of Grease Pencil changed a lot with addition of Vertex Painting.
So, it should be possible to follow the book without problem, today.
And except for Grease Pencil, it should be a decent reference during 2 years.
Because 2.83 will be first LTS.
Maybe some people will provide books up-to-date based on 2.83, in future months.
Maybe nobody will be interested in buying a book about 2.83 ; when 2.90 will be available in 4 months.