As you can tell from the full title, the main existing philosophies are Fichte's subjective take on Kant (in the Wissenschaftslehre) that denies the 'thing-in-itself' and Schelling's obscure Philosophy of Nature (1797). However, the book also engages with more empirical and psychological approaches to the study of the mind, including the idea of common sense philosophy, which he criticises for taking isolated propositions as starting points rather than seeing them in the 'light of the Absolute' (i.e. in the context of experience as a whole), but does not reject other than for that reason. This point is taken up again in the Phenomenology Preface, but it is expressed here in plainer language.
In general, Hegel's obscure mode of expression began with the middling essays of the Jena writings in the Critical Journal. I would thus recommend this book as an introduction to Hegel for its relative clarity. Other than that, if you want a clear introduction to Hegel, I'd recommend the early chapters of the Encyclopaedia Logic, which are included in Weiss's 'Hegel: the Essential Writings'. The translation by Cerf and Harris is as good as can be in the modern style, given the problems of language.