The "Virtuous Woman" is the linkage between books 29 and 30. Proverbs ends with an acrostic (22 verses beginning with the successive letters of the Hebrew alphabet) describing the "Virtous Woman." With the virtuous woman in mind the focus shifts to the life of Ruth. Ruth lives out the characteristics stated in Proverbs. When Boaz agrees to take Ruth's hand in marriage he uses the same Hebrew phrase occurring at the end of Proverbs to affirm Ruth's virtue.
The irony is the contrast between Proverbs which suggests one has to go looking to find the right woman and the book of Ruth where the right woman and man are divinely brought together. Both Boaz and Ruth appear to have been serving God and neither looking for a spouse directly or overly concerned with sealing a deal. Ruth had left home to be a foreigner in Israel instead of staying in Moab and looking for another husband after the passing of her first husband. Boaz was an older man who apparently had never married. The sense in this story is that Jesus connects the right people at the right time after both have made him the first priority in their personal lives.