TL,DR: Lyons' books are aimed at practitioners rather than university students, and the 1976 book by Peled and Liu is also very approachable compared to the other big names in DSP who were writing textbooks in that era. (I have a copy on my shelf but never really looked at it before.)

Peled/Liu includes a lot of FORTRAN example programs, some of which still look interesting due to approaches that don't tend to appear in later works. And you don't see any notes in Lyons on how to build an ALU for a dedicated DSP engine out of TTL chips.

So, viewed next to the contemporary graduate-level, math-heavy books by Oppenheim/Shafer and Rabiner/Gold, it actually is pretty reasonable to compare Peled & Liu to Richard Lyons or Steven W. Smith. They are all somewhat like an "Art of Electronics" for undergrads and practicing engineers who need to use DSP but who don't necessarily intend to specialize in it.

(I vouched for Onavo's dead comment below because it is true; digital watermarking is something that Liu did a lot of early work on. There's nothing about that in the edition of the book I have, though.)