You have read Meditations. You found some of it strange, some of it striking, a few entries you have already half-memorised. What now?
The temptation, at this point, is to read another translation of Meditations and call it progress. Don't. Marcus is a destination, not a starting point — the school had three centuries of argument behind it by the time he was writing in his tent. The interesting move is backwards, into the texts and arguments he was drawing on, and sideways, into the philosophers who disagreed with them.
Four follow-ups, in the order they make the most sense.
Discourses, Epictetus
Epictetus is the philosopher Marcus was reading. He was born into slavery and taught philosophy after he was freed, and his classroom comes through on the page in a way Marcus's notebook cannot. The Discourses are concrete, often funny, and unapologetic about the work. He talks about death and exile and being insulted and missing a meal as matters for a single technique — examining the impressions and asking what is yours. The Robin Hard translation, Oxford World's Classics, is the standard. Start with Book One.
How to Be Free, A.A. Long
A short, lucid book by the senior classicist of the field — half translation, half commentary on the Enchiridion. Long has spent fifty years on the Stoics and writes with the calm of someone who no longer needs to prove anything. If you found Epictetus difficult on first reading, this is the book that makes it click. It also models what serious philosophical commentary looks like — careful with the Greek, fair to the text, willing to disagree.
Philosophy as a Way of Life, Pierre Hadot
The essays here reframe what ancient philosophy was, which retroactively reframes what you have been doing when you read it. Hadot's claim — that ancient philosophy is a set of spiritual exercises, not a body of doctrine — is contested, but few people who take it seriously read the Stoics the same way afterwards. The essays on Marcus, in particular, are the best short pieces on Meditations in English. Read after Epictetus, not before.
Shame and Necessity, Bernard Williams
This is the one against the grain. Williams was a Cambridge philosopher who spent his career arguing that the Greeks knew something about ethical life we have lost — but he is no Stoic. He thinks the Stoic insistence on rational mastery over the emotions is a misreading of what an ethical life looks like, and he uses Homer and Sophocles to make the case. Read it not because it will convert you, but because no school survives contact with its strongest critics intact. The book will sharpen your sense of where the Stoics are right, and where they may not be.
After these four, you will know enough to choose your own next direction. Some people go further into the late Roman school — Seneca's letters, especially the ones to Lucilius. Others go back into the Hellenistic period proper, to Chrysippus and the early Stoa, where the technical philosophy lives. Others step out entirely, into the philosophers who answered the Stoics — Augustine, Aquinas, Spinoza, Nietzsche, Murdoch.
The point of a reading list is not to finish it. The point is to spend a few years in good company.