Klemperer's recordings of Beethoven are justly famous, especially his classic set of Fidelio. When it comes to the symphonies however, I find that Klemperer's methods don't stand up as well as his contemporary Wilhelm Furtwangler. Any person listening to a recording of Furtwangler will hear how different his approach really is. The best candidate for a Furtwangler Eroica is the 1944 wartime version, an inspirational account of this majestic symphony that has never been surpassed. The hallmarks of the great Furtwangler are tempo fluctuations, extreme passion, great weight of sound and a spiritual intensity unparalleled by any subsequent conductor.
Klemperer's performance is strictly objective but dogged by old-school "andante" tactics. Whereas for instance Toscanini's tempos are ferocious, Klemperer's is about giving every note and phrase it's full weight but lacking in Furtwangler's mercurial qualities. If you are used to the Toscanini interpretation, which is what Karajan, Szell and many others have taken up inspired by Toscanini, you will be bored stiff by Klemperer, especially his first movement, which is definitely more andante than allegro and takes nearly 17 without the exposition repeat. The funeral march is much more successful, although once again it's a very dry run-through instead of the sizzling emotions that Furtwangler uncovers. Klemperer's scherzo and finale never really take off, even though they are extremely well played.
Purchasing this Klemperer Legacy CD will also get you the string orchestra transcription of the Grosse Fugue on track 5. It is a titanic performance no doubt, but you'll ultimately stick to the original string quartet version which sounds far more abrasive and modern than a full string orchestra which can smooth out Beethoven's brutal contrasts in this masterpiece. My favorite Grosse Fugue performance is the early 1980's recording by the Lindsay Quartet.
These are classic recordings but you'll definitely want to stick to Karajan and Szell for the energetic frenzy that Klemperer does not provide. As I mentioned before, if you're looking for the true philosophical depth of the Eroica, there is always Furtwangler's amazing wartime reading that remains uniquely penetrating.