An e-mailer with a second opinion on Crusade in Europe:

Eisenhower recruited Harry Butcher (Commander in the Navy Reserve) to work with him and do a lot of his writing during and immediately after World War II. Take a look at Butcher’s own (heavily edited and censored by Eisenhower) book, MY THREE YEARS WITH EISENHOWER. The similarities in writing style are no less similar than the similarities between Bill Ayers and Barack Obama.
That doesn’t diminish Eisenhower’s demonstrated writing skills, but I wouldn’t place a lot of faith in Eisenhower writing any substantial portion of CRUSADE IN EUROPE.