What do you think of Louis-Philippe?

Was he ambitious for the throne and deliberately treacherous to his cousins, simply trying to make the best of a bad situation, or a bit of both?

Here is what I think. Louis-Philippe d'Orléans (1773-1850) was in many ways a prototype of contemporary neocons, in that he tried to merge the progressive ideals of the revolution with conservative values. Conservatism in the France of his day meant traditional monarchy; Louis-Philippe styled himself the "Citizen-King" and his "coronation" was a civil ceremony in the National Assembly, bereft of pomp, ritual and the blessing of the Church. This was to demonstrate his belief in the separation of Church and State, the opposite of Charles X's attempts to defend the Church from sacrilege. Charles bungled in his methods; he was not politically savvy and too much of a gambler. In the end, however, Louis-Philippe bungled, too, for he favored the wealthy industrialists over the needs and freedoms of the common people. And he had not begun his "reign" very auspiciously. Like many modern regimes, his assumption of the executive office was ratified by violence alone. The 1848 Revolution was even more bloody and violent than that of 1830, which had brought Louis-Philippe to power.

Otherwise, I think he was a decent man and I think his relationships with his wife and children were admirable.

That is interesting. I pretty much agree with this assessment.

In the novel Madame Royale, the portrayal of Louis-Philippe seemed somewhat more negative, though. But perhaps that was because he was seen mostly through the eyes of Marie-Thérèse, who understandably was not comfortable with the Orléans family.

Exactly. He was being seen through the eyes of MTC, who did not like him at all.