To some extent, one could say that Eisenhower's Modern Republicanism was a slight modification of Truman's Fair Deal. Some of the more extreme members of the GOP wanted to see Truman's policies dismantled altogether. They thought that government had become too big and was involving itself too much in the lives of individuals and businesses alike.

But Eisenhower was more pragmatic. He'd criticized Truman during the 1952 presidential election campaign for giving too much power to the state. Yet, at the same time, he still believed that some measure of government control was necessary for the maintenance of a stable economy and a just society. Eisenhower saw his approach as a middle way between the unfettered concentration of wealth and the unbridled power of the state. Truman's Fair Deal, on this reading, had gone too far towards the latter.

In its stead, Eisenhower favored what he thought was a more moderate alternative to the big government approach of the Fair Deal. Individual freedom and the market economy would be preserved, but the government would still have a role to play in protecting those who could not help themselves. To that end, Eisenhower even extended the role of government in some areas. He expanded Social Security, increased the minimum wage, and created the Department of Health, Education, and Welfare. He also supported the construction of low-cost public housing, though was prepared to spend much less than Truman.

Eisenhower also presided over an extensive improvement of the nation's infrastructure, something that would not have been out of place under Truman's Fair Deal. Yet as a Republican, Eisenhower was more instinctively averse to public spending than his predecessor. During his second term he used his veto to block a number of expensive programs supported by the Democratic Congress. Despite Eisenhower's best efforts, however, domestic spending continued to rise considerably.

I think that you should probably look in your text because it probably gives you a particular answer you are supposed to remember.

To me, there is not a huge difference between these two approaches.  The texts I use to teach out of in my college classes say the same.  They point out that both Truman and Eisenhower were interested in keeping the government pretty involved in the economy.

For example, Eisenhower did not try to end social security and labor laws and farm programs.  Instead, he actually extended them to some extent.

So, to me, the difference between the two is very small.  Eisenhower was more concerned with keeping costs down than Truman was, but he was not really interested in cutting government back to a large degree.

As one of my books says Eisenhower's

presidency in the end served to legitimate the New Deal by keeping its basic structure and premises intact during an era of prosperity.

So if your question is saying there's a big difference between the two, your book clearly disagrees with mine...