I find it hard to make up my mind about Lucius Annaeus Seneca. His writing makes me cringe, sometimes--particularly the deplorable Consolation to Polybius, addressed to the freedman of the Emperor Claudius. He often strikes me as sententious in the extreme, given to platitudes he was apparently inclined to foist upon his long-suffering friend, Lucilius, among others. One thinks of Ben Franklin composing Poor Richard's Almanac, but Seneca seems to lack Franklin's humor and (one hears, and hopes) Franklin's irony.
Then again, there is no doubting his ability. He must have been a kind of genius, to manage to administer (with Burrus) the Roman Empire during the times of Agrippina and Nero, to have survived the reigns of Tiberius and Claudius having suffered no more than exile to Corsica, write plays which formed the bases for many of those of Shakespeare, and to have had such an effect on European thought and literature for so many centuries.
Famously, he did not survive the reign of Nero; neither, of course, did Nero's mother as well as others, and one of the problems I have with Seneca is that he may have written Nero's apology for matricide to the Senate, or at least tacitly endorsed it by saying, it seems, nothing at all about it. He died quite nobly, though, if we can take the word of Tacitus on the subject, and Tacitus could be rather savage when he thought it necessary to be towards many of the great names of Roman history.
He is, of course, one of the great Roman Stoics, and was thought of fondly by many of the Christian Fathers, so much so that some forgotten person contrived to create a fraudulent correspondence between him and St. Paul (Seneca's brother was responsible for sending the mischievous Paul to Rome when Paul noted belatedly but somewhat eagerly under the circumstances, one would think, that he was a Roman citizen). He is considered to have humanized (even "Christianized") the stern Stoic creed along with Epictetus and Marcus Aurelius.
Perhaps his accumulation of wealth and power was a part of that humanizing. Some of the later Stoics came to consider such things, which should be indifferent to the sage, to be indifferent, yes, but also advantageous, provided one considered them ultimately unnecessary. Yet it is difficult to tolerate solemn pronunciations regarding the ills of wealth and power, or the fact that they mean nothing, from someone who was one the the wealthiest and most powerful men of his time and seemingly content to be one until Nero began to turn against him.
But he writes well, if in a somewhat artificial, highly stylized manner, regarding important things. It's difficult not to admire what he wrote and evidently thought.
It's also difficult to assess what kind of person he was based on the accounts we have of the time. How much of what survived may merely be malicious gossip? One reads good and bad things about him, but it seems the good outweighs the bad, in the end.
I suspect he was a "man of the world" who sincerely believed in what he wrote, but was very human, and driven by that which motivated the great of his time. He reminds me in some way of Cicero; vain, but essentially wise. Not a sage, no. Capable in any case of good counsel if not always of ideal conduct; interesting, influential, able. Generally admirable, as far as we human beings are or can be concerned.