Check Amazon Books and review 'Letters to No One in Particular' by Charles M Saunders. It is a discussion and illustration of Spinoza's "On the Improvement of the Understanding'. This short Treatise holds the key to opening the complexities in the "Ethics". Without an 'adequate' understanding of what Spinoza means by 'idea', which has nothing at all to do with today's usage, the enormity of the uniqueness of Spinoza's Epistemological revolution will go unnoticed. Spinoza is the 'only' thinker to both espouse and explicate the existence and operation of the human mind.
All the Best in your studies
Further suggestions for reading:
The Living Thoughts of Spinoza, by Arnold Zweig-- On Spinoza, by Diane Steinberg
Spinoza, by Roger Scruton-- Spinoza a Life, by Steven Nadler