I've owned Skolnik's "Radar Handbook" 2nd ed. for several years, and there are many copies of the 1st ed. in the area. I bought this new edition soon after it came out. In some respects it has been updated. However, in several areas I have found the earlier versions more helpful. Descriptions of recent developments have been added, but some of the material that has made the Radar Handbook a good reference has been taken out. Two examples:
The first ed. has 13 figures devoted to atmospheric absorption loss as a function of frequency, distance, and target altitude. They were reduced to 7 figures in the 2nd ed. In the 3rd ed. I could find no mention of atmospheric absorption. However, it discusses the propagation program AREPS.
The chapters on pulse doppler radar have about the same number of figures in the three editions. However, in the 3rd ed. fewer of the figures are for reference, and more are just to illustrate concepts. The four figures in the 2nd ed. that let you determine SNR for nonfluctuating (Marcum) or fluctuating (Swerling) targets were all replaced in the 3rd ed. with the approximation formulas due to Barton. That would be a good trade, except that eq. (4.25) has a serious typo: in the numerator, Km^{-1}(Pd,2ne) should be Km^{-1}(Pfa,2Npdi).
My recommendation is that if you work on radar design, you should own this book. However, if you have a previous edition, you should not give it away.