The level of analysis in Lewin's book varies from things that are relatively straightforward to quite advanced (graduate level). It's a very good book, but I'm not sure it's a good intro to music analysis on its own.
Schenker's analyses require an understanding of Schenkerian theory, basically a specialized graphical method that intends to show "deeper structure" that underlies larger pieces of music. Unfortunately, the graphic music analyses book is pretty much just a set of those graphs (with little explanatory text). Without a thorough background in the methodology used to produce those graphs (and what all the symbols mean), it's probably going to be hard to figure out what's going on or get much out of the graphs.
Anyhow, it really depends on what exactly you're interested in with music analysis. There are a lot of specialized books that could be introductions to various kinds of analysis, but I think there are relatively few that survey all of that well.
For example, one course that many undergraduates in music will take after basic harmony/counterpoint/intro theory courses is a class in musical form. That's generally also a course that introduces students to music analysis, as form gets at the "bigger picture" of how pieces are put together. One somewhat recent book that has a lot of details and examples (as well as an accompanying website with most of the examples for study) is William Caplin's Analyzing Classical Form. (That is itself an expansion on his book Classical Form that's more of a summary intended for an advanced audience.) But even that book has limitations, as it's really focused on music of the classical period (mostly Haydn, Mozart, Beethoven) for its examples. But the patterns it discusses are a baseline for analyzing much later music too.
But form is only one part of learning music analysis. As I said, I find it hard to recommend a book to serve as a general introduction, and many books with titles like "music analysis" are often quite limited, frequently focusing on harmonic theory or Schenkerian theory. Or they are mostly anthologies of pieces meant to be used as a basis for analysis with an experienced teacher as guide.
A few options that come to mind, though:
Deborah Stein's Engaging Music: Essays in Music Analysis is aimed at an (upper level) undergraduate audience and has mostly shorter analytical essays written by well-known music theorists specifically intended to be understood by those without a lot of experience in analysis. These give a broad survey of many different types of music analysis and ways of looking at music. (Unfortunately, the book is a bit pricey.)
Aside from that, Nicholas Cook's A Guide to Musical Analysis is a bit old (1992), but gives a broad survey of analytical ideas. However, it's also at times aimed a bit higher in level than the essays in the Stein book.
Many of Cook's ideas were challenging the status quo at the time the book was written, but a lot of his approaches have become mainstream since then. Another book written around the same time that takes a more traditional approach to an overview of analysis is Dunsby and Whittall's Music Analysis: In Theory and Practice.