I can't recommend this book too highly for serious readers of Hegel and especially of Hegel's _Science of Logic_.
After two introductory chapters the third chapter, which is by far the longest, give a quite comprehensive commentary on the Quality section, the first three chapters, of the SL. The first two chapters of the SL go from Being to True Infinity. The third chapter explains how True Infinity collapses. This collapse more or less continues through the Quantum section. With the Measure section things start turning around, and the beginning is made of re-establishing True Infinity on a sound foundation so that it doesn't collapse.
People looking for help in reading the SL might be considering Houlgate's recent book on the subject. I haven't seen the book, but those who have think well of it. According to its description, the first part of the book is an introduction to and general consideration of Hegel's logic. The book then concludes with a detailed commentary on the first two chapters, from Being to True Infinity. It seems unfortunate that Houlgate didn't extend this commentary through the third chapter so that the whole beginning would be presented. Presumably one will finish the book not knowing that True Infinity will collapse at virtually the very moment it is established.
Chapters 4 and 5 of Wallace's book deal, respectively, with The Doctrine of Essence and The Doctrine of the Notion. These two chapters are much shorter than chapter 3 and cover more material. And Wallace always stays close to the text. So his presentation is very selective here. The first half of his chapter 4 is quite difficult. But this probably has to do with the fact that the first half of the Doctrine of Essence is quite difficult. The Doctrine of Essence concludes in a very interesting way, and Wallace's chapter then becomes correspondingly interesting. Wallace's fifth chapter, although very selective in what it deals with, is particularly illuminating and helpful.
But this points to a major problem in English language Hegel scholarship. A full commentary on the SL, similar to Harris's commentary on the Phenomenology or Petry's commentary on the Philosophy of Nature, is definitly required. I don't know that I would wish such a major task on my worst enemy. But Wallace would undoubtedly be well qualified for this undertaking. Not only does he possess a very fine understanding of Hegel's logic, but he also possesses a clear, pleasant, readable writting style.
In the sixth chapter Wallace deals with Hegel's system as a whole. It is quite remarkable how he is able to present such a comprehensive account of the complete system in the course of a single chapter. But more importantly he shows how the system is rooted in the logic. A good analogy might be that True Infinity is to the system as a whole similar to what an acorn is to an oak tree. So with this last chapter Wallace provides a very panaramic view of Hegel's system that is quite impressive.
So then, as I said, I can't recommend this book too highly for serious readers of Hegel.