Take a look at what the CISSP covers, if it seems like a big jump for you, pick up an SSCP book (I used the first edition of this book). It's a good midway point between the Sec+/CEH and the CISSP.
Version 2: SSCP v2 - Amazon
Version 3: SSCP v3 - Amazon
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I passed the exam last January 2019 using the materials listed above. There's an updated version of the Official SSCP Study guide as well but the release date is still on May 14, 2019.
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My recommendation is to download the SSCP Exam Outline (Dated Nov 1 2018) PDF on (ISC)2's website and check if you know all the topics listed. :)