In the United States the Lectionary is based on the New American Bible (NAB). The NAB is published by the United States Conference of Catholic Bishops (USCCB), originally in 1970.
The Lectionary was revised in the 1990s, after new translations of the New Testament (1986) and Psalms (1991) appeared. (The revised books of the NAB are known as the RNAB.) The readings for the Propers (saints' days, etc.) were expanded, also.
When the Holy See reviewed the revised text (submitted by the bishops in 1992), it was found that the 1991 translation of the Psalms was so defective that it could not be used even as a "base text" for the Lectionary; and the 1986 New Testament had to be amended (one major problem: so-called "inclusive" language).
Thus the revised Lectionary had to undergo extensive "repairs"; consequently, in the late 1990s, several US bishops and Vatican experts together amended the Lectionary text, to correct the defective translations.
Nearly ten years after it was first submitted to the Holy See, the new two-volume Lectionary appeared in print. The eventual version as approved (subject to review after five years) has been the only edition of the Lectionary permitted for use in the United States since May 19, 2002, when it became mandatory. No other scripture translations are to be used for the US Lectionary. The bishops have now appointed a committee for the first review.
A most unfortunate anomaly in all this is that there is no edition of the Bible at present that corresponds to the Lectionary. All the current editions of the complete NAB contain the Revised 1986 New Testament (unamended) and Revised Psalms (1991) that the Holy See found defective.
This is a complex situation -- and is especially confusing to people who are looking for a reliable Catholic Bible, because imprimaturs (literally ,"let it be printed") were granted to these books by presidents of the USCCB (Cardinal James Hickey  and Archbishop Daniel Pilarczyk ) before they were judged defective by the Holy See.
Thus the ironic and anomalous situation wherein the complete NAB scripture text, currently in print and available in various editions, does not "match" the Lectionary text. --Source
Oh dear. Oh my. I prefer my Ignatius Bible (RSV 2nd-Catholic Edition) though I do have a couple of copies of the NAB and had no idea that the issue of the Lectionary was so complex. God bless our Bishops and may they get this sorted out under the direction of the Holy Spirit.