Good intro DSP book, presenting everything at a good pace. Also nice for those who want a bit of review. Might be a bit too introductory at times though.
As an introductory DSP text, DSP First covers quite a bit of ground: 1)a review of complex number manipulation and phasor representation 2)common concerns with sampling, aliasing, and hardware implementation 3)the important concepts of linearity and time invariance 4)Fourier and FFT 5)signals & systems review (convolution, cascading, impulse response, step function, impulse signal, cascading) 6)comparisons of signals/systems in the time domain, frequency domain, and z-domain 7)and all manner of filters (FIR, bandpass, feedback, feed forward, etc.)
Because I read a preliminary edition of the text, there were math, figure misidentification, or typographical errors in various places, but overall the text was still understandable in most cases. The largest drawbacks of this particular version of the text were a lack of an index or problem set answers. I'm not sure if those improvements have been made in subsequent printings, but I would hope so.