Hii guys I have a qus I was doing my study with GMAT official guide and I also got GMAT official guide reviews books( data insights , verbal reasoning and quantitative reasoning)too when I saw the material I realised that half of the GMAT official guide reviews books (data insights, verbal reasoning and quantitative reasoning) are already coved by GMAT official guide ....... Why I needed reviews books? Are they worth it ? And only GMAT official guide is good ? ..... Because those reviews books adding extra expenses. Please help me out with this