We present photometric , spectroscopic and weak lensing analysis of the large-scale structure and dynamics of the most X-ray luminous galaxy cluster known , RX J1347-1145 , at z = 0.451 . We spectroscopically confirmed 47 new members with LDSS3 on the Magellan telescope . Together with previously known members , we measure a new velocity dispersion of 1163 \pm 97 km s ^ { -1 } . The mass inferred from our velocity dispersion is M _ { 200 } = 1.16 ^ { +0.32 } _ { -0.27 } \times 10 ^ { 15 } M _ { \odot } , with r _ { 200 } = 1.85 Mpc , under the assumption of a singular isothermal sphere . We also present a weak lensing analysis using deep CFHT data on this cluster , and find a deprojected mass of 1.47 ^ { +0.46 } _ { -0.43 } \times 10 ^ { 15 } M _ { \odot } within r _ { 200 } , in excellent agreement with our dynamical estimate . Thus , our new dynamical mass estimate is consistent with that from weak lensing and X-ray studies in the literature , resolving a previously claimed discrepancy . We photometrically detect and spectroscopically confirm another massive cluster with \sigma = 780 \pm 100 km s ^ { -1 } and M _ { 200 } = 3.4 ^ { +1.4 } _ { -1.1 } \times 10 ^ { 14 } M _ { \odot } \sim 7 Mpc south-west of RX J1347-1145 , which we refer to as RXJ1347-SW. Our spectroscopic survey reveals a possible excess of galaxies in velocity space in the region between RX J1347-1145 and RXJ1347-SW ; comparing with simulations , this excess appears consistent with that expected from a large filamentary structure traced by galaxies connecting these two clusters .