3.5 stars, rounded up to 4.
It is a well written, interesting and informative book.
Unfortunately it is a bit uneven (too basic in some parts - only at beginner/intermediate level at best), but overall a nice book.
Some portions of the book are brilliantly executed and thoroughly enjoyable (such as the ones dealing with the hard problem of consciousness and the debate over mind-body duality/relationship, and the ones dealing with issues of causality, predictability, the problem of induction, the concept of "Universal Law", determinism versus indeterminism, and free will).
On the not-so-positive side, the section on logic is average and quite basic in contents, and the section on ethics is quite uninspiring and it even deteriorates (in the sub-section about "social ethics") into a thinly disguised apologism of unfettered laissez-faire economic liberalism.
Recommended as a non-technical, intermediate-level introduction to some typical subjects of philosophical inquiry. Nothing earth-shattering, but a quite solid and interesting, easy and informative read.