In music there is often more than one way of naming a particular note, e.g., F# is the same note as Gb. Such notes are called enharmonic notes.
This final piece is another example of the 12 Bar Blues. It contains many accidentals, so take it slowly at first to be sure you are playing the correct notes.
Having completed this book, you are now ready to proceed to one of the many books in the Progressive piano and keyboard series.