Seder Nasim is the shortest of the six orders of the Mishna comprising only seven of the sixty-three masechtot and “only” 578 of the over 4,200 Mishnayot in in the Talmud Bavli. And two of the seven masechtot, Nedarim and Nazir, have little to do with women, ostensibly the theme of the seder. Masechet Nedarim dealing with laws of promises and vows is included because the previous masechet, Ketubot devotes more than a chapter to cases when one spouse takes a vow forbidding themselves from giving or deriving benefit from the other or taking a vow to forbid one’s spouse from certain activities. That leads to the broader discussion of the laws of vows i.e. masechet Nedarim.
From Nedarim we move to a specific type of a neder, that of a nazirite vow. As masechet Ketubot segues into masechet Nedarim, masechet Sotah follows on the heels of masechet Nazir. “Whoever sees a sotah in her degradation shall take a vow of abstinence from wine” (Sotah 2a). 
The story of a sotah is a tragic one. It begins when a husband suspects his wife of adultery - how sad that we should come to this - and in front of two witnesses warns her not to be alone with the suspected 'adulterer'. And lo and behold they are found to be alone. She denies having committed adultery and she may very well be telling the truth but we really have no way of knowing that. The Torah ordains we go through an elaborate and very degrading ordeal, to either encourage her to admit to having had an affair, or to confirm her innocence. The Torah, in a most unique assertion, tells us that after she drinks “the bitter water” we will be given a sign of her innocence or guilt. 
If she admits to adultery her husband divorces her but no other punishment is given, save that she loses the alimony she would normally receive upon divorce. If she maintains her innocence she drinks a concoction of Torah parchment mixed with water and dirt and we wait. Either her body will contort leading to her death or she will be blessed with many children having been falsely accused of adultery (despite her inappropriate early actions). 
Either way this is a terrible ordeal to endure and even to witness. Those who do, our Sages, suggest should consider becoming a nazir, withdrawing somewhat from society and its attendant frivolity. We need look no further than the office party to understand the connection between wine and sexual immorality. 
The first six chapters of the masechet spell out in great detail the ordeal of the sotah but contain a number of fascinating digressions; most significantly how much, if any, Torah it is appropriate to teach women. We will PG return to this subject in due course.
The last three chapters of the masechet are one long digression detailing which mitzvoth that require speech i.e. prayer, birchat hamazon, shema, court administered oaths, birchat kohanim, must be said in Hebrew and which may be said in any language. The discussion flows from the ruling that the declaration of the sotah may be said in any language. 
The enumeration of the various mitzvoth into these categories of language leads to a broader discussions of the mitzvoth in question. The most “current” is that of exemptions from army service - a subject we will also PG return to in due course. This discussion follows from the ruling that the kohen mashuach milchama, the chief army chaplain, must address the people in Hebrew only. 
Towards the end of the masechet the Mishna notes how the deaths of many of our Talmudic Sages marked the end of an era; i.e. “when Rabbi Akiva died, the honour given to Torah died” with him. Unlike the end of the marriage of the sotah these ends were preceded by periods of greatness.
The last Mishna of the masechet records the teaching of Rav Pinchas ben Yair that religious growth is a ladder that one must climb step by step - jump too high, too fast and you will fall off. It is this teaching that forms the core of the Mesilat Yesharim, the Path of the Just, perhaps the most famous book of ethical piety in our tradition, written by the 18th century Italian kabbalist Rav Moshe Chaim Luzzato[1].

[1] It is almost by accident that the Mesilat Yesharim survived as most of the writings of Rav Luzzatto (Ramchal) were burned due to suspicion of heresy, seeing him and his writings as similar to Shabbtei Tzvi. The legacy of many is much different from what anyone could have predicted during their lifetime.