A few books that I found very good information on Tet are "Snafu: Great American Military Disasters" by Geoffrey Regan and "Battle 100" by Michael Lanning.
I learned a great deal from these 2 books.
As far as a perspective from the North Vietnamese Bui Tin who was an NVA officer defected and his interview was publishes in "The Wall Street Journal" in 1995. He is asked about Tet. Below is his answer. From the link below.
"Q: What was the purpose of the 1968 Tet Offensive?
A: To relieve the pressure Gen. Westmoreland was putting on us in late 1966 and 1967 and to weaken American resolve during a presidential election year.
Q: What about Gen. Westmoreland's strategy and tactics caused you concern?
A: Our senior commander in the South, Gen. Nguyen Chi Thanh, knew that we were losing base areas, control of the rural population and that his main forces were being pushed out to the borders of South Vietnam. He also worried that Westmoreland might receive permission to enter Laos and cut the Ho Chi Minh Trail. In January 1967, after discussions with Le Duan, Thanh proposed the Tet Offensive. Thanh was the senior member of the Politburo in South Vietnam. He supervised the entire war effort. Thanh's struggle philosophy was that "America is wealthy but not resolute," and "squeeze tight to the American chest and attack." He was invited up to Hanoi for further discussions. He went on commercial flights with a false passport from Cambodia to Hong Kong and then to Hanoi. Only in July was his plan adopted by the leadership. Then Johnson had rejected Westmoreland's request for 200,000 more troops. We realized that America had made its maximum military commitment to the war. Vietnam was not sufficiently important for the United States to call up its reserves. We had stretched American power to a breaking point. When more frustration set in, all the Americans could do would be to withdraw; they had no more troops to send over. Tet was designed to influence American public opinion. We would attack poorly defended parts of South Vietnam cities during a holiday and a truce when few South Vietnamese troops would be on duty. Before the main attack, we would entice American units to advance close to the borders, away from the cities. By attacking all South Vietnam's major cities, we would spread out our forces and neutralize the impact of American firepower. Attacking on a broad front, we would lose some battles but win others. We used local forces nearby each target to frustrate discovery of our plans. Small teams, like the one which attacked the U.S. Embassy in Saigon, would be sufficient. It was a guerrilla strategy of hit-and-run raids.
Q: What about the results?
A: Our losses were staggering and a complete surprise;. Giap later told me that Tet had been a military defeat, though we had gained the planned political advantages when Johnson agreed to negotiate and did not run for re-election. The second and third waves in May and September were, in retrospect, mistakes. Our forces in the South were nearly wiped out by all the fighting in 1968. It took us until 1971 to re-establish our presence, but we had to use North Vietnamese troops as local guerrillas. If the American forces had not begun to withdraw under Nixon in 1969, they could have punished us severely. We suffered badly in 1969 and 1970 as it was."
I also see some similarities between the Battle of the Bulge and the Tet Offensive.