Very interesting to read this so shortly after Marcus Aurelius's Meditations. Both proclaim stoic values; but where Aurelius is humble, inquisitive and positive in his outlook, Seneca comes off much more as a grumpy old man, telling the kids that they're living their lives wrong!
Aurelius presents stoicism very neutrally; "here are the stoic values" he says, "by following them I have found happiness, and maybe others can as well". There is a gentleness and a distinct lack of preaching; others may be struggling with any sorts of problems including materialism. If you can help them and instruct them without causing harm or being a jerk, then do so. But if not, don't worry about it! Don't let others throw you off your own internal balance. And he provides many aphorisms to help you maintain that balance.
Seneca on the other hand, launches immediately into "look at these bloody youths! Spending all their time getting their hair cut, lounging about, being idle and self-absorbed! If only they were true stoics like me they'd be happy and they wouldn't be bothering me!" It's honestly pretty funny; it's the absolute classic, tried-and-true trope of the bitter old man, shouting at kids to get off his philosophical lawn. There is a distinct lack of self-awareness as Seneca lacks many of the values he seemingly endorses, or at best has twisted them beyond recognition to suit his own needs.
The second essay contained in this book is possibly an even worse offender, in which he spends the entire document telling his own mother how to live her life happily, again with no hint of irony or self-awareness. "Hey, it's a real shame you're such a stupid woman or you might have been able to understand philosophy, then your life would have been so much better".
Still an interesting read for historical context, and there are some elements of true stoic wisdom in here, even if Seneca doesn't fully get them himself.