I think Simple may be the least rewarding / most diluted of the Ottolenghi books if you already have a full spice cabinet and are not daunted by a long list of ingredients.
The techniques in any of his books are not complicated, though he does tend to fuss it up for seemingly no reason (you’ll be able to cut through that).
ETA: I added a few links on the 20 years of Ottolenghi thread; this one may be of interest:
